Fuels, Lubricants, Coolants, and Filters PDF - Fundamentals of Service

TENTH EDITION Check Out All Of Our Titles In The FUNDAMENTALS OF SERVICE Series! Here are a few of the titles in this series: Hydraulics Service, testing, and maintenance guide for hydraulic systems in off-road vehicles, trucks, and buses Shop Tools A basic guide showing the right tool for each type of job and its proper use Electronic and Electrical Systems Service, testing, and maintenance guide for electronic and electrical systems in off-road vehicles, trucks, and buses Identification of Parts Failures A highly-illustrated failure analysis guide for automotive and off-road vehicle parts Engines Service, testing, and maintenance guide for power trains in off-road vehicles, trucks, and buses Welding The fundamentals of welding, cutting, brazing, soldering, and surfacing of metals Power Trains Service, testing, and maintenance guide for power trains in off-road vehicles, trucks, and buses Our FUNDAMENTALS OF SERVICE Series brings together all the technical information you need and combines it with clearly written and amply illustrated instructional aids for many types of mechanical systems, their components, the tools needed, and repair procedures Our catalog includes the FARM BUSINESS MANAGEMENT, FUNDAMENTALS OF SERVICE, FUNDAMENTALS OF MACHINE OPERATION and COMPACT EQUIPMENT series. To download the latest catalog or for order information, please visit: www.JohnDeere.com/publications PUBLISHER DEERE & COMPANY JOHN DEERE PUBLISHING one John Deere Place Moline, IL 61265 http://www.JohnDeere.com/publications Fundamentals of Service (FOS) is a series of manuals created by Deere & ACKNOWLEDGEMENTS: Company. Each book in the series is conceived, researched, outlined, edited, and published by Deere & Company, John Deere Publishing. John Deere gratefully acknowledges help from the following groups: Authors are selected to provide a basic technical manuscript that could be American Association for Agricultural Engineering and Vocation Agriculture; edited and rewritten by staff editors. American Petroleum Institute; American Society of Agricultural Engineers (ASAE); Borg Warner Corp.; Dana Corp.; Ethyl Corp.; Federal-Mogul corp.; Gulf Oil Corp.; Imperial Oil Ltd.; National Board of Fire Underwriters; Nation Fire Protection Assoc.; National LP-Gas Association; Purdue University Extension Service; Shell Oil Co.; Society of Automotive Engineers; Standard Oil Co.; Texaco, Inc.; TRW Replacement Division; Union Carbide Corp.; University of Missouri Experiment Station. Thanks also to a host of John Deere people for their valuable suggestions and comments. HOW TO USE THE MANUAL: This manual can be used by anyone — experienced mechanics, shop trainees, vocational students, and lay readers. Persons not familiar with the topics discussed in this book should begin with Chapter 1 and then study the chapters in sequence. The experienced person can find what is needed on the “Contents” page. Each guide was written by Deere & Company, John Deere Publishing staff in cooperation with the technical writers, illustrators, and editors at Almon, Inc. — a full-service technical publications company headquartered in Waukesha, Wisconsin (www.almoninc.com). FOR MORE INFORMATION: This book is one of many books published on agricultural and related subjects. To download the latest catalog or for order information, please visit: www.JohnDeere.com/publications We have a long-range interest in Vocational Education Copyright © 1970, 1974, 1979, 1980, 1985, 1987, 1992, 2000, 2008, 2015. Printed in U.S.A. DEERE & COMPANY, Moline, IL/Tenth Edition/All rights reserved. ISBN 0-86691-428-5 This material is the property of Deere & Company, John Deere Publishing, all use and/or reproduction not specifically authorized by Deere & Company, John Deere Publishing is prohibited. 01/27/2016 Fuels, Lubricants, Coolants, and Filters FUNDAMENTALS OF SERVICE Fuels, Lubricants, Coolants, and Filters ISBN 0-86691-428-5 FOS5810NC (2016) (ENGLISH) A training guide to the how’s and whys of modern fuels, lubricants, coolants, and filters Deere & Company PRINTED IN U.S.A. Introduction To download the latest catalog or for order information please visit: www.JohnDeere.com/publications Check out all of our titles in the FUNDAMENTALS OF FUNDAMENTALS OF SERVICE (FOS) SERVICE series! Here are a few of the titles in this series: Fundamentals of Service (FOS) is a series of manuals created by Deere & Company. Each book in the series is Air Conditioning conceived, researched, outlined, edited, and published Service, testing, and maintenance guide for air by Deere & Company, John Deere Publishing. Authors conditioning systems in off-road vehicles, trucks, and are selected to provide a basic technical manuscript that buses. could be edited and rewritten by staff editors. Hydraulics HOW TO USE THE MANUAL: This FOS manual can Service, testing, and maintenance guide for hydraulic be used by anyone — experienced mechanics, shop systems in off-road vehicles, trucks, and buses. trainees, vocational students, and lay readers. The instructions are written in simple language so that they Hydraulic Diagnostics Systems can be easily understood. Service, testing, and troubleshooting guide for hydraulic systems in off-road vehicles, trucks, and buses. Persons not familiar with the topics discussed in this book should begin with Chapter 1 and then study the chapters Shop Tools in sequence. The experienced person can find what is A basic guide showing the right tool for each type of job needed on the “Contents” page. and its proper use. Each guide was written by Deere & Company, John Electronic and Electrical Systems Deere Publishing staff in cooperation with the technical Service, testing, and maintenance guide for electronic and writers, illustrators, and editors at Almon, Inc. — a electrical systems in off-road vehicles, trucks, and buses. full-service technical publications company headquartered Identification of Parts Failures in Waukesha, Wisconsin (www.almoninc.com). A highly illustrated failure analysis guide for automotive This material is the property of Deere & Company, and off-road vehicle parts. John Deere Publishing. All use and/or reproduction not Engines specifically authorized by Deere & Company, John Deere Service, testing, and maintenance guide for power trains Publishing is prohibited. in off-road vehicles, trucks, and buses ACKNOWLEDGEMENTS: Welding John Deere gratefully acknowledges help from the The fundamentals of welding, cutting, brazing, soldering, following groups: American Association for Agricultural and surfacing of metals. Engineering and Vocation Agriculture; American Power Trains Petroleum Institute; American Society of Agricultural Service, testing, and maintenance guide for power trains Engineers (ASAE); Borg Warner Corp.; Dana Corp.; Ethyl in off-road vehicles, trucks, and buses. Corp.; Federal-Mogul corp.; Gulf Oil Corp.; Imperial Oil Ltd.; National Board of Fire Underwriters; Nation Fire Our FUNDAMENTALS OF SERVICE series brings Protection Assoc.; National LP-Gas Association; Purdue together all the technical information you need and University Extension Service; Shell Oil Co.; Society combines it with clearly written and amply illustrated of Automotive Engineers; Standard Oil Co.; Texaco, instructional aids for many types of mechanical Inc.; TRW Replacement Division; Union Carbide Corp.; systems, their components, the tools needed, and repair University of Missouri Experiment Station. Thanks also to procedures. a host of John Deere people for their valuable suggestions and comments. OUO1023,00040C5 -19-11JAN16-1/1 012716 PN=2 Contents Page Page FUELS INTRODUCTION................................................01-1 COMPRESSION AND FUELS...........................01-4 ANSWERS ENERGY CONTENT..........................................01-5 ANSWERS TO CHAPTER 1 QUESTIONS........06-1 SELECTING FUEL FOR GASOLINE ANSWERS TO CHAPTER 2 QUESTIONS........06-1 ENGINES.......................................................01-6 ANSWERS TO CHAPTER 3 QUESTIONS........06-1 SELECTING FUEL FOR LP-GAS ENGINES...01-13 ANSWERS TO CHAPTER 4 QUESTIONS........06-1 SELECTING FUEL FOR DIESEL ENGINES...01-14 ANSWERS TO CHAPTER 5 QUESTIONS........06-2 STORING FUELS.............................................01-20 STORING GASOLINE FUELS.........................01-21 APPENDIX STORING DIESEL FUELS...............................01-26 WEIGHTS AND MEASURES — STORING LP-GAS FUELS..............................01-29 METRIC TO U.S............................................. A-1 HANDLE FUEL SAFELY—AVOID FIRES........01-30 WEIGHTS AND MEASURES — U.S. PREPARE FOR EMERGENCIES....................01-31 TO METRIC.................................................... A-3 TEST YOURSELF............................................01-31 FUELS, LUBRICANTS, COOLANTS, AND FILTERS................................................. A-4 LUBRICANTS INTRODUCTION................................................02-1 ENGINE OILS.....................................................02-3 GEAR OILS......................................................02-21 DIFFERENTIAL OILS.......................................02-24 TRANSMISSION FLUIDS................................02-25 HYDRAULIC FLUIDS.......................................02-28 LUBRICATING GREASES...............................02-29 TEST YOURSELF............................................02-31 COOLANTS INTRODUCTION................................................03-1 PARTS OF LIQUID COOLING SYSTEMS.........03-3 ANTIFREEZE.....................................................03-5 COOLING SYSTEM.........................................03-10 MAINTENANCE OF THE COOLING SYSTEM......................................................03-12 SUMMARY.......................................................03-17 TEST YOURSELF............................................03-17 DIESEL EXHAUST FLUID (DEF) INTRODUCTION................................................04-1 DIESEL EXHAUST FLUID (DEF) TANK............04-4 DIESEL EXHAUST FLUID (DEF).......................04-5 TEST YOURSELF..............................................04-7 FILTERS INTRODUCTION................................................05-1 TYPES OF FILTRATION SYSTEMS..................05-2 TEST YOURSELF............................................05-16 Original Instructions. All information, illustrations and specifications in this manual are based on the latest information available at the time of publication. The right is reserved to make changes at any time without notice. COPYRIGHT © 2015 DEERE & COMPANY Moline, Illinois All rights reserved. A John Deere ILLUSTRUCTION ™ Manual Previous Editions Copyright © 1970, 1974, 1979, 1980, 1985, 1987, 1992, 2000, & 2008 i 012716 PN=1 Contents ii 012716 PN=2 FUELS DXP02701 —UN—23FEB11 INTRODUCTION DXP05426 —UN—12MAY15 In this chapter you will learn about compression of explains the importance of selecting the proper fuel and gasoline, diesel, and LP-gas engines. This chapter also storing fuel. Continued on next page KN52281,0000E84 -19-29MAY15-1/3 01-1 012716 PN=5 FUELS DXP00112 —UN—23DEC08 Fig. 1 — How a Four-Stroke Cycle Engine Works (Spark-Ignition Shown) If you purchase a new machine today, you will find that (B) COMPRESSION—Mixture is compressed by the the engine is designed for use with a certain fuel. For upstroke of the piston. Both the intake and exhaust are example, if it is a tractor equipped with a diesel engine, closed. you have no choice but to use diesel fuel. It will not operate on gasoline or LP-gas. (C) POWER—Compressed mixture is ignited by the spark plug. Expanding gases force the piston to the bottom of This situation has not always been true. Two-fuel engines the cylinder. The valves remain closed. that started on gasoline and operated on kerosene or distillate were quite popular at one time. Some are still (D) EXHAUST—Exhaust piston on the upstroke forces in use, but they are not as efficient as engines designed burned gases from the cylinder through the open exhaust for use with one fuel. valve. Figure 1 shows the basic operation of a spark ignition four stroke engine: (A) INTAKE—Air-fuel mixture is drawn into cylinder from the carburetor through the open intake valve by the downstroke of the piston. Continued on next page KN52281,0000E84 -19-29MAY15-2/3 01-2 012716 PN=6 FUELS DXP00123 —UN—23DEC08 Fig. 2 — Spark-Ignition and Diesel Engines Compared A—Spark Ignition Engine B—Spark D—Diesel Engine F— Air C—Air-Fuel Mixture E—Fuel From this it might appear that there is no fuel selection qualities. This is because of the difference in the way the problem once you have selected your engine. But the fuel is ignited in each type. quality of each fuel you use is directly related to the maintenance required and to the performance you can On the spark ignition engine, the air-fuel mixture enters expect. the cylinder and is compressed, and a spark ignites the air-fuel mixture. Then, too, the quality of fuels and their ingredients keep changing. Various terms are used to describe these On a diesel engine air only enters the cylinder and is changes, such as “octane rating,” “sulfur content,” “cetane compressed, fuel is sprayed in and the air-fuel is ignited rating,” and “volatility.” You need to know what these terms from the heat of the compression (Fig. 2). mean in order to understand how these changes apply to The important points you need to know about selection of your engine. An example is the gradual increase in the each fuel are discussed under these headings: octane rating of regular gasoline over a period of years. Is it of any value to you as a user of a gasoline engine? 1. Selecting Fuel For Gasoline Engines 2. Selecting Fuel For Lp-Gas Engines In addition, spark-ignition engines require fuels with 3. Selecting Fuel For Diesel Engines certain qualities, while diesel engines require other fuel KN52281,0000E84 -19-29MAY15-3/3 01-3 012716 PN=7 FUELS COMPRESSION AND FUELS 1 1 2 2 3 16 3 4 4 5 to 5 6 7 1 6 8 7 9 DXP05288 —UN—05MAY15 A B C Fig. 3 — Fuels Must Be Matched With Engines of Proper Compression Ratios A—Diesel 16-to-1 Ratio B—Gasoline 8.5-to-1 Ratio C—LP-Gas 9-to-1 Ratio In discussing each of these fuels, the term “compression LP-gas, which is still a lighter fuel, can have a compression ratio” is used frequently. It is important that you ratio of 9 to 1 or higher. understand its meaning. The higher the compression ratio, the more the fuel-air Compression ratio is the relation between the total volume mixture is compressed and the higher the pressure inside the engine cylinder when the piston is at its greatest inside the cylinder before the fuel burns. If the fuel burns distance from the cylinder head (Fig. 3), compared to properly, higher compression greatly increases the power the volume when the piston has traveled closest to the output of the engine because more of the fuel energy is cylinder head. developed into useful power. Diesel engines ignite fuel by heat resulting from a However, each fuel has its limit on how much it can be compression ratio of 16 to 1. compressed and still burn properly when ignited in a With lighter fuels such as regular gasoline, the spark-ignition engine. compression ratio is about 8 to 1 and as high as 9 to 1. Continued on next page KN52281,0000E85 -19-29MAY15-1/2 01-4 012716 PN=8 FUELS DXP05289 —UN—05MAY15 A B C Fig. 4 — How Combustion Knock Occurs in a Gasoline Engine For example, kerosene burns evenly in an engine with a compression ratio of 4 to 1 and supplies a smooth flow of power. But if it is used in an engine with a compression ratio of 7.5 to 1, it will burn unevenly and cause the engine to “knock” (Fig. 4). A — Spark Begins, Air-Fuel Mixture Burning. B — Flame Advances Smoothly, Compressing and Heating the End-Charge. DXP05290 —UN—13MAY15 C — End-Charge Suddenly Ignites with Violence, Producing a Knock. During knock, fuel ignites next to the spark plug and builds up tremendous pressure on the unburned fuel as shown. This pressure then causes spontaneous combustion of the unburned fuel, causing a small explosion or knock. Fig. 5— Damaged Ring Combustion knock damaged this piston (Fig. 5) and broke the second ring (Fig. 5-D). The top ring (Fig. 5-E) is stuck and broken. If regular gasoline is used in place of kerosene, it will burn satisfactorily in an engine with a 7-to-1 compression ratio Fuel knock is a serious problem because it may damage or higher. However, it will not burn satisfactorily in an valves, pistons, and bearings. It also results in a loss of engine with a 6-to-1 or lower compression ratio. power. KN52281,0000E85 -19-29MAY15-2/2 Fuel Type Btu/Gallon ENERGY CONTENT Diesel 138,700 Gasoline contains an average of about 125,000 Btu per Regular Gasoline 125,000 gallon. The actual energy content varies as much as 4% Premium Gasoline 125,000 from season to season and from batch to batch, according to the U.S. EPA. Gasohol (10% Ethanol + 90% 120,900 Gasoline) Aviation Gasoline 120,200 Liquefied Natural Gas 90,800 Ethanol 84,600 Methanol 64,600 Table 1— Fuel Energy Content KN52281,0000E86 -19-29MAY15-1/1 01-5 012716 PN=9 FUELS SELECTING FUEL FOR GASOLINE ENGINES DXP00114 —UN—23DEC08 Fig. 6 — Gasoline Fuel System A—Air Intake C—Fuel Tank E—Fuel Intake B—Air-Fuel Mixture D—Fuel Pump and Filter F— Carburetor Gasoline as a fuel is still widely used for farm and PROPER OCTANE RATING industrial machines. But in recent years diesel engines have become more prominent in these applications. We Engine Compression Fuel Approx. Octane No. will discuss diesel fuels later. Ratio (Approx.) Gasoline (Regular) 7.0–9.0 to 1 A factor that helped make gasoline a popular fuel was Gasoline (Premium) 9.0–10.0 to 1 the raising of the “octane rating.” When oil companies raised the octane, engines with higher compression ratios LP-Gas were developed to take advantage of the efficiency made Butane 8.0 to 1 100–110 possible by using the higher-octane fuels. Propane 9.0 to 1 110–120 Almost all new, one-fuel gasoline engines are designed Combining the octane ratings of the Motor Method and the Research to operate on regular-grade unleaded gasoline. If you Method, then dividing by 2, derives the octane numbers shown in the purchase regular-grade unleaded gasoline from a reliable table. This gives you the average between the two. These numbers dealer, you are almost certain to have the grade and are typically found at the pump. quality of fuel needed for your engine. But it is important that you understand the principal qualities that make the This table also gives the compression ratios and octane ratings expected with modern fuels. fuel satisfactory as compared to low-grade (fleet) gasoline or even as compared to higher grades of gasoline. Table 2— Compression Ratios and Octane Ratings of Spark-Ignition Engines The important qualities are: The most important characteristic of gasoline is its 1. Proper octane rating octane rating, the measure of how resistant gasoline 2. Easy starting is to premature detonation in an internal combustion 3. High oxidation stability and freedom from gum engine, also known as knocking. The octane rating is your 4. Freedom from foreign matter, including water and dirt assurance of getting a fuel with adequate antiknock. Your 5. Use of fuel additives operator’s manual tells you what the minimum octane 6. Volatility rating should be for your engine. Compare it with the octane rating of the fuel supplied by your dealer. If you don’t understand the meaning of “octane number rating,” the following discussion will help. The octane rating is a method of comparing the antiknock qualities of fuels used in spark-ignition engines with standard test fuels. The American Society for Testing and Materials (ASTM) has established it. The lowest number on the octane scale is zero. Continued on next page KN52281,0000E87 -19-29MAY15-1/7 01-6 012716 PN=10 FUELS Fuels near that end of the scale have a bad tendency EASY STARTING to knock; kerosene is one of them. Fuels with the least tendency to knock have higher octane numbers, some Provision for easy starting is “built in” by both the gasoline even higher than 100. LP-gas and super-premium and engine manufacturers. gasoline are examples of these. The gasoline property that is most important in engine You may see two octane ratings mentioned in your starting and performance is volatility. The volatility of a operator’s manual. For example, one manual states, “The gasoline affects engine operation in a number of ways. gasoline should have a minimum octane number rating If it is too low, insufficient vapor can affect starting. On of 85 (Motor Method) or 93 (Research Method).” This is the other hand, a gasoline with too high a volatility is confusing unless you understand that, while both methods apt to cause carburetor icing and also vapor lock under use much the same test procedures and equipment, there adverse atmospheric conditions. A balance must be are certain differences, such as engine speeds, spark struck between these extremes. The volatility is controlled advance, and intake air temperatures. For example, and measured by a laboratory distillation test and by a with the Research Method the test engine runs 600 rpm Reid vapor pressure test. (revolutions per minute); with the Motor Method the test In summer, oil companies blend their gasoline so volatility engine runs 900 rpm. This results in a difference in the (its tendency to evaporate) is low. With the higher summer octane number ratings between the two test methods. temperatures, your engine will start without the gasoline For the same fuel, the Research Method octane number having high volatility. In winter, your engine will be slow is always higher than the Motor Method octane number, to start unless the gasoline vaporizes readily; so oil but not by any fixed amount. The spread may vary from companies blend gasoline for higher volatility. narrow to wide, depending on the makeup of the fuel. If you have held over a supply of gasoline from summer If you are given the octane rating of gasoline and only one to winter, you may experience hard starting. The only number is given with no mention of the Method, you can controls you have over volatility are to buy small quantities assume it is the Research Method octane number. But of gasoline and store them properly so as to keep down gasoline pumps are often marked with the average of the evaporation. This is discussed later in this chapter under Research Method and Motor Method for consumers (M+R “Storing Gasoline Fuels.” / 2). You would be wise to look at the octane ratings on STORAGE STABILITY the gas pumps to determine which is highest and lowest. The tendency of gasoline to form gum in storage is an The terms “premium,” “regular,” and “low-grade” are rough indication of its oxidation stability. comparative measures of octane ratings. Most engines on farm and industrial machines use regular grade. Most Oxidation stability is tested by an ASTM method, which manufacturers design their engines to use regular-grade measures the stability of gasoline under accelerated gasoline. But regular-grade fuel has increased in octane oxidation conditions. rating. And manufacturers have increased compression ratios in their engines to get the higher efficiencies made In this test, a special container equipped with a pressure possible by higher-octane fuels. gauge is partially filled with gasoline; the remaining volume of the bomb is filled with oxygen at 100 pounds You can use premium-grade gasoline, but there is usually per square inch (690 kilopascals) pressure. The bomb no advantage since most engines are not designed (do is placed in a water bath at 212°F (100°C), and the time not have a high enough compression ratio) to benefit from in minutes from the start of the test until the pressure the higher octane rating, and premium gasoline costs drops 2 pounds in 15 minutes is reported as the induction more per gallon. period. The length of the induction period is an indication of the oxidation resistance of the sample, since the Low-grade (fleet) fuel is rarely used anymore, and it is pressure drop is indicative of the start of the oxidation of not a good choice, because it develops less power and the unstable components in the sample. Most modern causes engine knock on hard pulls. gasoline has induction periods that exceed 240 minutes. There are several ways of improving the octane rating This method was developed when unstable, of gasoline. For years the common way was to add thermally-cracked gasoline stocks were widely used. Its tetraethyl lead (TEL), but environmental concerns have usefulness has decreased with the trend to gasoline dictated the use of other additives. Unleaded gasoline stocks of greater inherent stability. uses hydrocarbon fractions of high octane number to get the same results. Antioxidant additives that minimize gum formation and lead antiknock decomposition also adequately stabilize Gasoline containing tetraethyl lead is now less available. most of today’s gasoline. Engines designed to run on leaded fuel may experience valve recession and increased ring wear if run on unleaded gasoline. Continued on next page KN52281,0000E87 -19-29MAY15-2/7 01-7 012716 PN=11 FUELS FREEDOM FROM FOREIGN MATTER Higher gasoline octane numbers (more resistance to knock) can be achieved in two ways: Freedom from dirt and moisture is mostly a matter of how gasoline is handled and stored. Most distributors By refining processes, such as catalytic reforming, of petroleum products are well equipped and careful in which convert low-octane hydrocarbons to high-octane handling fuels to avoid dirt. The dirt and moisture problem hydrocarbons. usually develops during handling and storage on the farm By using antiknock additives. or job site. This too is discussed later in this chapter. Selection of the route to be used is dictated by cost GASOLINE ADDITIVES AND THEIR FUNCTIONS and usually involves a combination of processing and antiknock additives. Additives have played an important role in gasoline since fuel containing tetraethyl lead was first marketed in 1923. The octane number requirement of an engine depends on how its design and operating conditions affect the Additives have become essential ingredients of modern temperature and pressure of the end gas in the engine. gasoline, except for tetraethyl lead. Widespread use of most additives has occurred during the past two decades. An engine’s tendency to knock varies with the compression ratio, spark advance, manifold vacuum, Additives are used to raise octane number and to combat engine speed, combustion chamber design, air-fuel ratio, surface ignition, spark plug fouling, gum formation, rust, altitude, and atmospheric conditions. carburetor icing, deposits in the intake system, and intake valve sticking. For many years, tetraethyl lead (TEL) was used as a highly effective antiknock agent for the majority of gasoline In most cases, a chemical compound satisfies one of blends. The precise mechanism by which TEL controls these functions. In some cases, however, an additive may knock is not known despite extensive research. perform more than one job. For example, a carburetor detergent may serve as an anti-icing agent and a Because of ecological and health concerns, TEL is corrosion inhibitor. scarcely used anymore. ANTIKNOCK ADDITIVES When a gasoline containing lead antiknock alone is burned in a spark-ignition engine, it produces nonvolatile Antiknock compounds are used to combat the tendency combustion products. Therefore, commercial antiknock of gasoline to knock in a spark-ignition engine. Ideally, fluids contain scavenging agents (ethylene dibromide gasoline should burn smoothly and evenly in the and/or ethylene dichloride) that transform the combustion combustion chambers of an engine. products of the antiknock into forms that are vaporized readily from hot engine surfaces. These scavengers are However, gasoline is composed of hundreds of different included as a part of any antiknock compound containing hydrocarbons, many of which may react rapidly and very lead. violently when compressed and heated in the presence of air. After ignition, the spreading flame front in an engine’s The new unleaded gasoline uses hydrocarbon fractions of combustion chamber further compresses and heats the high octane to replace the lead additives and so provide a fuel-air mixture ahead of it. Under these conditions, some “cleaner” fuel. The addition of alcohol will also raise the hydrocarbons in the unburned end gas may undergo octane level. chemical reactions prior to normal combustion. The products of these reactions may then self-ignite. When NOTE: Some older engines that were designed to run on this happens, the end gas burns very rapidly—at a rate leaded fuel may experience piston ring wear and of 5 to 25 times that of normal combustion—causing valve recession when run on unleaded gasoline. high-frequency shock waves that produce the sharp metallic noise called knock. Methylcyclopentadienyl manganese tricarbon (MMT) has been used for many years in Canada and more recently Besides producing an objectionable sound, a knocking in Australia to boost octane. It also helps old engines engine may give less power and poorer fuel economy. designed for leaded fuel run on unleaded fuel without Severe knock also tends to increase piston-ring wear and additional additives to prevent valve problems. However, to cause overheating of valves, spark plugs, and pistons, MMT reduces the effectiveness of emission controls shortening their service life and promoting destructive and increases pollution from motor vehicles. It is also pre-ignition. suspected to be a dangerous neuro and respiratory toxin. Factors Affecting Knock DEPOSIT MODIFIER ADDITIVES The presence or absence of knock in an engine is Deposit modifier additives combat surface ignition and determined by two factors: spark plug fouling by altering the chemical character of combustion-chamber deposits. Antiknock quality (octane number) of the gasoline. Octane number requirement of the engine. Continued on next page KN52281,0000E87 -19-29MAY15-3/7 01-8 012716 PN=12 FUELS peak pressure during the compression stroke of the Surface Ignition engine cycle. Surface ignition occurs when the fuel-air charge is ignited In extreme cases, surface ignition can heat deposits by hot spots within the combustion chamber; this includes and engine parts to the point where ignition occurs glowing deposits. progressively earlier in the cycle. Such runaway To the operator, surface ignition usually reveals itself either pre-ignition can quickly burn holes in pistons or exhaust as sporadic high frequency knocking called “wild ping” or valve faces. as low-frequency noises, similar to those produced by Phosphorus compounds are widely used as deposit worn main bearings, called “rumble.” modifiers. These additives suppress surface ignition by Wild ping results when the surface-ignited flame front raising the temperature required to initiate glowing of causes the pressure and temperature in the unburned deposits and by reducing the rate of heat release from portion of the fuel-air charge to rise much faster than in oxidation of the deposits. normal combustion. Consequently, the unburned fuel-air Some refiners use a boron compound to combat surface mixture is stressed far beyond its antiknock quality and ignition. In addition, boron promotes the antiknock action knock results. of TEL in certain types of gasoline. This results from the Rumble, on the other hand, is a form of non-knocking ability of the boron to prevent normal sulfur concentrations combustion. It occurs when ignition from a number of in gasoline from reducing the antiknock effectiveness of sources produces a very rapid pressure rise and high TEL. Continued on next page KN52281,0000E87 -19-29MAY15-4/7 01-9 012716 PN=13 FUELS Spark Plug Fouling Combustion products tend to deposit on spark plug insulators (Fig. 7) when an engine is operated under light-duty low-temperature service, such as in stop-and-go driving. Subsequent acceleration raises the temperature of these deposits. Since the electrical resistance of the deposit decreases with rising temperature, the deposits may become sufficiently conductive to prevent the plugs from firing. Such misfiring usually occurs at high engine speeds or during acceleration in the middle-speed range. To alleviate spark-plug fouling, phosphorus compounds in gasoline fuel change the deposits to forms having much DXP05292 —UN—05MAY15 higher electrical resistance over a wider temperature range. ANTIOXIDANTS Antioxidants are added to gasoline to prevent gum formation during the normal life of the finished fuel. Fig. 7 — Deposit Fouling of Spark Plug Gum forms in gasoline when the unstable hydrocarbons combine with oxygen (oxidize) or with each other (polymerize). The type of crude oil from which the A—Deposit gasoline is produced, the refining processes used, the storage temperature, the extent to which air is present, and the length of storage influence gum formation. Several types of hydrocarbon-soluble compounds are When gum is formed, it produces a varnish-like deposit used as rust inhibitors. These include various fatty that tends to coat and clog the fuel lines, carburetor jets, acid amines, sulfonates, alkyl phosphates, and amine and intake manifold, and may also cause intake valves phosphates. Most of them act by coating metal surfaces to stick. with a very thick protective film that keeps water from contacting the surfaces. This “surface active” property The oxidation stability of gasoline can be improved by can also help to prevent carburetor icing and the buildup various refining treatments, such as caustic washing, of carburetor deposits. acid washing, partial hydrogenation, and contacting with activated clays. However, such processing is usually quite ANTI-ICING AGENTS expensive and tends to rob the gasoline of the unsaturated, Ice can interfere with engine operation either by plugging high-octane, olefinic hydrocarbons. Therefore, refiners fuel lines or by upsetting carburetion through ice formation frequently find it more economical to use small quantities in the air or fuel passages. Plugging of fuel lines stems of an antioxidant to supplement or replace processing. from water present in the fuels. Freezing of water vapor, Antioxidants retard the oxidation and polymerization of however, causes carburetor icing, from the air the engine the unstable hydrocarbons. Although the mechanism of breathes. this action is not well defined, antioxidants are believed When a cold engine is started under certain atmospheric to act as “chain-breakers” in the various oxidation and conditions, the most critical being from 30° to 50°F (–1° to polymerization reactions. 10°C) at relative humidity above 65%, the cooling effect ANTIRUST AGENTS of fuel vaporizing in the carburetor causes the moisture in the air to condense and freeze on the chilled carburetor Rusting and corrosion can lead to severe problems in surfaces. When the throttle is almost completely closed storage tanks, lines, and the fuel systems of engines. for idling, this ice tends to bridge the small gap between the throttle blade and the throttle body, cutting off the air For example, leaks may develop in corrosion-weakened supply and stalling the engine. Opening the throttle for tanks or lines, or particles of rust may impede engine restarting breaks the ice bridge but does not eliminate operation by clogging filters and carburetor jets. In the possibility of further stalling before the engine and addition, a rust particle lodged on the seat of a carburetor’s carburetor have fully warmed up. needle valve may cause the float bowl to overflow, followed by engine stalling due to “flooding.” Two general types of carburetor anti-icing additives: Rusting and corrosion of iron and bimetallic parts are freezing-point depressants promoted by small amounts of water and air dissolved in surface-additive agents gasoline. Water can enter the fuel system of an engine by condensation in the fuel tank or by being pumped in with These anti-icing additives are used in gasoline to avoid the the gasoline. annoyance of cold-weather stalls during engine warm-up. Continued on next page KN52281,0000E87 -19-29MAY15-5/7 01-10 012716 PN=14 FUELS FUEL TYPE DYE COLOR The freezing-point depressants serve as antifreezes, AVGAS (aviation gasoline) 100LL (100 octane, low Blue combating carburetor icing in much the same way as lead) antifreeze provides winter protection in an engine’s Non-taxed diesel for agricultural use Red cooling system. These anti-icing additives, which include alcohol, glycols, and a formamide, reduce ice formation Table 3 — Fuel Energy Content by lowering the freezing point of the water vapor in the air. DYES The surface-active agents provide a different kind of Dyes are added to gasoline to indicate the presence of protection. With these agents, ice particles are allowed antiknocks, promote sales appeal, and identify various to form. However, the additive provides a coating that makes or grades of gasoline. Dye is included in leaded tends to prevent these particles either from sticking to fuel to identify its use as a motor fuel only and to warn each other or from building up on the metal surfaces of against its misuse for heating or cleaning purposes. the carburetor. Instead, most of the ice particles pass harmlessly through the carburetor into the intake manifold. Gasoline dyes are hydrocarbon-soluble organic Examples of this type of additive are amides, amines, and compounds that are selected for the color they impart to amine or ammonium salts of phosphates. the fuel. Some freezing-point depressants and, to a lesser Dye concentration depends on the intensity of color extent, some surface-active agents are also effective in desired by the refiner to meet a color standard. preventing ice plugging of fuel lines. CARBURETOR DETERGENTS ALCOHOL When an engine is idling, nonvolatile fuel components, together with contaminants from exhaust and crankcase Some producers, to form a fuel blend called gasohol, fumes drawn in through the air cleaner, tend to accumulate have blended alcohol with gasoline. The fuel is usable on the inside walls of the carburetor just below the throttle in most gasoline-fueled engines, and there may be an blade. By interfering with airflow and upsetting the air-fuel economic advantage to some, especially cooperatives. ratio, these deposits can lead to rough idling with frequent However, there are some aspects of the fuel you should stalls and reduced performance and fuel economy of the weigh carefully if you use an alcohol-gasoline blend. engine. Alcohol may attack rubber and some plastic products like Detergent additives are used to prevent deposit buildup fuel lines, gaskets, filters, and fittings. It also corrodes in carburetors and to remove deposits already formed. some metal parts in fuel systems. There is usually a drop The effectiveness of these detergents, which include in power when gasohol is burned in an engine. Alcohol amides and alkyl amine phosphates, stems from their raises the vapor pressure of gasoline in tanks, and lowers surface-active properties. the amount of air needed for an explosion. This makes gasohol more vulnerable to flashing (igniting with a spark). Continued on next page KN52281,0000E87 -19-29MAY15-6/7 01-11 012716 PN=15 FUELS OXYGENATES Oxygenates, when blended with gasoline, add oxygen to the fuel and reduce the amount of carbon monoxide and unburned fuel in the exhaust gas. Reformulated gasoline (RFG), or oxygenated gasoline, is produced by adding DXP05293 —UN—30APR15 oxygen-bearing compounds such as MTBE, ethanol, and ETBE to gasoline. Oxygenate blending is mandatory in many areas throughout the U.S. MTBE has been widely used as an octane-increasing additive since the use of lead in gasoline was banned. MTBE is being phased out and banned in many areas. It contains carcinogenic compounds and has been Fig. 8 — Use Only a Good Grade of Gasoline associated with groundwater contamination. Ethanol is the most common oxygenate blended with gasoline. Approximately half the gasoline sold in the US VOLATILITY is blended with ethanol primarily derived from corn. A Gasoline is more volatile than diesel fuel, Jet-A, or common ethanol-gasoline mix is known as E10, containing kerosene. The desired volatility of gasoline depends on 10% ethanol. The most extensive use of ethanol is in the ambient temperature and is adjusted with the use of Brazil, where the ethanol is derived from sugar cane. additives. Ethanol can be converted into an additive known as ETBE. In the U.S., volatility is regulated in urban regions as a This additive has both advantages and disadvantages means to reduce the emission of unburned hydrocarbons when compared to ethanol. Currently, it is used on a much by creating summer and winter blends. In colder climates, smaller scale than ethanol. too little volatility may cause difficulty when starting an engine. In warmer climates, too much volatility may result in vapor lock where combustion fails to occur. KN52281,0000E87 -19-29MAY15-7/7 01-12 012716 PN=16 FUELS SELECTING FUEL FOR LP-GAS ENGINES DXP05294 —UN—05MAY15 Fig. 9 — LP-Gas Fuel System A—Vapor E—Vapor-Air Mixture to Power H—Vapor L— Liquid Fuel B—Liquid Engine I— Return Water C—Converter (Vaporizes Fuel) F— Air Intake J— Fuel Strainer D—Hot Water From Engine G—Carburetor K—Fuel Tank (Pressurized to Keep Fuel in Liquid Form) LP-gas may be: to as high as 10 to 1. Both gases have a high octane rating ranging from about 95 for butane to as high as All Propane 125 for propane. With such a high octane rating, they All Butane are well fitted to high-compression engines. In fact, A Combination Of The Two Gases higher compression enables these fuels to supply power Today, LP-gas is either all propane or mostly propane economically even though they actually contain less because of the high demand for butane in the chemical energy per gallon than gasoline, kerosene, or “tractor fuel.” industry. Both products are gases and cannot be used Machines equipped for LP-gas use the vapor in the top through a regular gasoline tank and carburetor because of the fuel tank (Fig. 9) for easy starting because it is they must be stored and handled in high-pressure already vaporized. containers to keep them in liquid form. Butane boils at approximately 33°F (1°C), while propane boils at There is very little you can do about selecting LP-gas fuel –44°F (–42°C). When confined to a closed container, the except to deal with a reliable distributor. You are entirely pressure varies with the outside temperature. Butane dependent on your distributor to supply fuels that are develops 37 pounds per square inch (255 kilopascals) relatively free of sulfur compounds and other contaminants pressure at 100°F (38°C), while propane develops 195 that may cause difficulties such as filter plugging and pounds per square inch (1340 kilopascals) pressure at valve failures. However, customers seem to have had the same temperature. very little bad experience from impurities in LP-gas fuel. An LP-gas engine is similar to a gasoline engine but is For cold weather operation, your dealer may have a designed with a higher compression ratio—about 8 to 1 different blend of LP-gas than for warmer weather. KN52281,0000E88 -19-29MAY15-1/1 01-13 012716 PN=17 FUELS SELECTING FUEL FOR DIESEL ENGINES DXP05295 —UN—05MAY15 Fig. 10 — Diesel Fuel System A—Air Compressed C—Fuel Tank E—Fuel Filters B—Injection Nozzles D—Fuel Transfer Pump F— Injection Pump There is a saying “Diesel engines will burn anything.” It is By comparison, in the diesel engine, air alone is taken true that they will burn a variety of fuels; in fact, powdered into the cylinder and compressed. The fuel is injected at coal was the first fuel used for diesel engines. high pressure through a nozzle into the compressed air From this, you may gain the wrong impression that charge, and is ignited by the heat of this charge. selecting fuel for your diesel engine is simply supplying During injection, it is vital that the atomized fuel particles anything it will burn; but diesel fuel selection is far more are fully mixed with the molecules of hot compressed air critical than this. In fact, you need to know more about the so that the maximum possible number of ignition points qualities of diesel fuels than about the quality of gasoline. are created throughout the charge to provide early and Before studying diesel fuel selection, we must first uniform ignition. understand how a diesel engine works. Figure 2 shows Depending on the compression ratio, the temperature of the operating principles of a 4-stroke cycle diesel engine the intake air, and the injection timing, the temperature as compared to a gasoline engine. and pressure of the compressed air at the time the fuel Note that there is no spark plug to start the fuel burning. enters the cylinder may be as high as 1200°F (650°C) and Instead, the air is compressed until it is so hot that fuel 900 pounds per square inch (6200 kilopascals). injected into it will start burning spontaneously (Fig. 10). The speed and power output of the diesel engine is The compression ratios for diesel engines are much higher regulated by the amount of fuel injected per stroke. At any than for spark-ignition engines. This extra compression given engine speed, the amount of air taken into the engine of the air provides high enough temperatures (900° to usually remains constant regardless of load, and there is 1200°F) (480° to 650°C) that the fuel is ignited by itself generally sufficient air to burn the amount of fuel injected. when sprayed into the cylinder. This means that the overall air-fuel ratio in a cylinder The average compression ratio for diesel tractors is must always be leaner than that required to burn the approximately 16 to 1. They vary from as low as 14 to 1 fuel completely. However, since diesel engines smoke to as high as 20 to 1. on occasion, incomplete burning will occur under certain conditions. The most likely causes of black smoke are THE DIESEL CYCLE faulty fuel injection, air restriction, turbocharger lag, or over-fueling. White smoke, which may occur during idling In a spark-ignition engine, the charge of fuel and air is or other cool-engine operation, is caused by unburned or taken into the cylinder as a mixture, compressed, and is partially burned fuel. ignited by the spark plug. Continued on next page KN52281,0000E89 -19-01JUN15-1/7 01-14 012716 PN=18 FUELS To obtain an understanding of the major requirements PETROLEUM DIESEL for a diesel fuel, it is necessary to consider the diesel combustion process. Most diesel fuel is produced from petroleum and is sometimes referred to as petrodiesel to distinguish it from It would be reasonable to assume that ignition occurs the other diesel sources. instant the fuel particles contact the high-temperature air within the combustion chamber. However, this does When burnt, diesel releases about 15% more energy than not happen. Pressure measurements made during the gasoline and is generally simpler to refine than gasoline. It compression and power strokes indicate that there is a does contain higher levels of pollutants and must undergo slight delay between the start of fuel injection and the time additional filtering that contributes to a higher cost at times. that sufficient energy is released by burning to increase The higher energy content of diesel results in higher levels the pressure above that obtained by compression of the of carbon dioxide released per-gallon of fuel burned. air alone. However, the diesel-powered vehicles generally have The ignition delay is an important factor in diesel engine significantly better fuel economy that offset the per gallon combustion. Too long a delay period at high engine emissions. The result is that engines using diesel fuel loads results in too rapid an increase in pressure when release significantly lower levels of carbon dioxide than the fuel starts to burn. The rate of pressure rise may equivalent gasoline engines. become so rapid at high engine loads that knock or rough One pollutant in diesel fuel is sulfur. Diesel in the US engine operation will occur. For many years this sudden has long been “dirtier” than European diesel, where increase in pressure was attributed to accumulation of tax incentives and strict standards have dramatically fuel in the combustion chamber. However, evidence is decreased the level of sulfur in diesel fuels. The U.S. has mounting to support the theory that a long delay period recently adopted stricter standards to reduce the level of allows more time for certain chemical reactions to take sulfur in diesel fuels. High levels of sulfur in diesel reduce place in the fuel-air mixture before ignition occurs. These the effectiveness of particulate filters and emission control reactions result in products that burn very rapidly, causing equipment on vehicles. excessively rapid pressure rise. With a short delay period, ignition apparently occurs before these reactions have To ensure the proper characteristics and to maintain the proceeded far enough to cause too rapid burning. Also, uniformity of product, the refining processes used to with a cold engine and low intake air temperatures, too produce diesel fuel must be closely controlled. long a delay period produces misfiring and uneven or incomplete combustion, with consequent smoke and loss The American Society for Testing Materials (ASTM) has of power. established a classification of diesel fuels for various types of diesel engine service. Although the ignition delay is influenced by engine operating conditions, it depends primarily on the The major grades covered in the ASTM “Specification for hydrocarbon composition of the fuel and, to a lesser Diesel Fuel Oils” are: extent, on its volatility. No. 1-D Diesel Fuel No. 2-D Diesel Fuel No. 4-D Diesel Fuel GRADEa MAX SULFUR DESCRIPTIONb No. 1-D S15 15 ppm A special-purpose, light middle distillate fuel for use in diesel engine applications with frequent and widely No. 1-D S500 500 ppm varying speeds and loads or when abnormally low operating temperatures are encountered. Higher volatility than that provided by Grade No. 2 fuels. No. 1-D S5000 5000 ppm No. 2-D S15 15 ppm A general-purpose, middle distillate fuel for use in diesel engines, especially in applications with relatively No. 2-D S500 500 ppm high loads and uniform speeds, or in diesel engines not requiring fuels having higher volatility or other properties specified in Grade No. 1-D fuels. No. 2-D S5000 5000 ppm No. 4-D A heavy distillate fuel, or a blend of distillate and residual oil, for low- and medium-speed diesel engines in applications involving predominantly constant speed and load. Table 4 — Diesel Fuel Grades a Further ASTM specifications exist for heavier fuel oils Grade 5 and 6 (residual), and marine diesel fuels. b Based on the appendix to ASTM D 975. The D 975 is inconsistent in its description of the applications of the different fuel grades given in the scope statement and in the appendix. The limiting requirements by the ASTM for these grades engine design and operation materially affect the type of of diesel fuels are shown in table 4. Some of these fuel best suited for an engine. fuel characteristics are discussed next. Remember that Continued on next page KN52281,0000E89 -19-01JUN15-2/7 01-15 PN=19 012716 FUELS KINEMATIC WATER CARBON DISTILLATION COPPER CET- DIESEL VISCOSITY SUL- FLASH CLOUD AND RESIDUE ASH % TEMPERATURE, STRIP ANE FUEL AT 40°C FUR POINT POINT SEDIMENT ON 10% MASS 90% VOLUME CORRO- NUM- GRADE CENTISTOKES PPM % VOL. RESIDUE RECOVERED SION BER (MM2/S) Min Max Max Max Max Min Max Min Max Max Max Min No. 1-D S15 No. 1-D 100°F — 550°F A 0.05 0.15 0.01 1.3 2.4 500 No. 3 40 S500 (38°C) (288°C) No. 1-D 100°F a — 550°F 0.05 0.15 0.01 1.3 2.4 5000 No. 3 40 S5000 (38°C) (288°C) No. 2-D S15 No. 2-D 125°F 540°F 640°F A 0.05 0.35 0.01 1.9 4.1 500 No. 3 40 S500 (52°C) (282°C) (338°C) No. 2-D 125°F 540°F 640°F A 0.05 0.35 0.01 1.9b 4.1 5000 No. 3 40 S5000 (52°C) (282°C) (338°C) No. 4-D 125°F — — — — — A 0.05 0.01 2.00 20000 30 (52°C) Table 5 — ASTM Limiting Requirements for Diesel Fuels a For cold weather operation, the cloud point should be specified at 10°F (6°C) above the tenth percentile minimum ambient temperature at which the engine is operated except where fuel heating is provided. b When cloud point less than 10°F (6°C) is specified, the minimum viscosity shall be 1.7 mm 2/s and the mini- mum 90% distillation temperature shall be waived. CETANE NUMBER reference blends differing by not more than 5 cetane numbers. Then, knowing the cetane numbers of the The method for determining the ignition quality of diesel bracketing blends and the compression ratios required by fuel in terms of cetane number is similar to that used for the fixed delay period for both the reference blends and determining the antiknock quality of gasoline in terms of the sample fuel, the cetane number of the sample can octane number. be obtained by calculation. As in the case of the octane number scale, the scale of The cetane number of a diesel fuel depends primarily on cetane number represents blends of two pure hydrocarbon its hydrocarbon composition. In general, the aromatic reference fuels. Cetane is a hydrocarbon with very hydrocarbons are low in cetane number, the paraffin has high ignition quality, and was chosen to represent the high cetane numbers, and the naphthenes fall somewhere top of the scale with a cetane number of 100. The in between. Thus, it is apparent that the base stocks hydrocarbon called alphamethylnaphthalene has very low and refining processes used in making diesel fuels are ignition quality, and was chosen to represent the bottom all-important in determining ignition quality. The refiner is of the scale with a cetane number of zero. Blends of constantly faced with the problem of blending stocks to these two hydrocarbons represent intermediate ignition achieve adequate ignition quality without sacrificing other qualities, and their cetane number is the percentage of necessary characteristics, such as pour point and volatility. cetane in the blend. For example, a reference fuel blend containing 30% cetane and 70% alphamethylnaphthalene The ignition quality of a diesel fuel can also be improved by is assigned a cetane number of 30. the use of additives, such as amyl nitrate. The relationship between the cetane number of a diesel fuel and the The engine used in cetane number determinations performance of a diesel engine should not be confused is a standardized (ASTM) single-cylinder, with the relationship between the octane number of variable-compression ratio engine with special loading gasoline and the performance of a spark-ignition engine. and accessory equipment. In gasoline engines, raising the octane number improves Under test, the compression ratio of the test engine is potential engine performance via increased compression varied until combustion starts at top dead center. With ratio or supercharging, and the octane number requirement the start of fuel injection timed at 13°BTDC and with is usually fixed by the full-load demand of the engine. combustion timed to start at top dead center, an ignition delay period of 13° (2.4 milliseconds at 900 rpm) is In diesel engines, the requirements for good ignition produced. quality during starting and light load operation at low temperatures establish the desirable cetane number. This procedure is then repeated using reference fuel blends until the unknown fuel is bracketed between two Continued on next page KN52281,0000E89 -19-01JUN15-3/7 01-16 012716 PN=20 FUELS In general, high-cetane fuels permit an engine to be A D started at lower air temperatures, provide faster engine warm-up without misfiring or white smoke, reduce the rate of formation of varnish and carbon deposits, and eliminate combustion roughness or diesel knock. However, too high cetane numbers may lead to incomplete combustion and exhaust smoke if the ignition delay period B E is too short to allow proper mixing of the fuel and air within the combustion space. The difference between octane numbers (gasoline) and cetane numbers (diesel fuel) is shown in Figure 11. DXP05297 —UN—05MAY15 SULFUR C F Diesel fuel contains varying amounts of sulfur, depending on the crude oil source, refining processes, and grade. Sulfur tends to be more prevalent in the higher boiling range fractions. The U.S. EPA, under authority of the G Clean Air Act, regulates sulfur content. It is considered the most important fuel property regulated by the EPA Fig. 11 — Octane and Cetane Number Are Opposites HIGHWAY DIESEL FUEL REGULATIONS A—Gasoline (must burn E—Cetane Number October 1993—Sulfur limit of 500 ppm (0.05% wt.). This evenly) F— Measure of Fast, fuel, commonly referred to as the low sulfur diesel fuel, was B—Octane Number Spontaneous Combustion C—Measure of Ability to Resist G—Opposites introduced to reduce sulfate particle emissions to meet the Detonation 1994 emission standards for heavy-duty highway engines. D—Diesel Fuel (must burn fast) June 2006—Diesel fuel with sulfur limit of 15 ppm becomes available for highway use. This ultra low sulfur fuel (ULSD) enables catalyst-based emission control devices such as VOLATILITY particulate filters and NOx adsorbers. This is necessary to meet the 2007–2010 emission standards for heavy-duty The distillation characteristics of a diesel fuel are engines, as well as Tier 2 standards for light-duty engines. essential for good combustion in the diesel engine. The characteristics are achieved by a careful balancing of the light and heavy petroleum fractions during the refining process. The components of the blend, which boil at the NONROAD DIESEL FUELS highest temperatures, have higher heating values than do June 2007—Sulfur limit of 500 ppm becomes effective for the lighter fractions. nonroad, locomotive, and marine fuels. Although a lot of heavy fractions in the final product may June 2010—Sulfur limit of 15 ppm becomes effective for improve good fuel economy, it can be harmful due to nonroad fuels. Use of the ULSD will enable advanced deposit formation within the engine. emission control systems for meeting the Tier 4 nonroad Too many light fractions may provide easier engine emission standards. starting and more complete combustion under a variety of June 2012—Sulfur limit of 15 ppm becomes effective for engine conditions. However, the light ends are generally locomotive and marine fuels. low in ignition quality. Moreover, they do not release as much energy per gallon as do the heavier fractions. High sulfur content can become a problem in diesel engine operation at low temperatures and during Volatility characteristics also influence the amount and intermittent engine operation. Under these conditions, kind of exhaust smoke and odor. The temperatures at where more moisture condensation can take place, using which 10%, 50%, and 90% of the fuel is evaporated during fuels containing excessive amounts of sulfur may cause a distillation test are important control points in achieving cold corrosion and increased engine wear. best volatility balance. Ultra low sulfur diesel fuel (15 ppm) and low sulfur diesel POUR POINT fuel (500 ppm) should be used. If diesel fuel with greater Diesel fuel must be able to flow at the lowest expected than 5000 ppm sulfur content is used, reduce the service atmospheric temperatures. The lowest temperature at interval for engine oil and filter by 50%. DO NOT use which the fuel ceases to flow is known as its pour point. diesel fuel with sulfur content greater than 1000 ppm. Continued on next page KN52281,0000E89 -19-01JUN15-4/7 01-17 012716 PN=21 FUELS and sometimes in delivery inspections. Gravity may also As fuel temperature decreases toward the pour point, the be measured in “degrees API.” The higher the API gravity fuel becomes sluggish and harder to pump through the of the fuel, the lower its density or specific gravity. In fuel supply lines, fuel filters, and injection system. general, the refiner’s choice of blending stocks and refining The pour-point temperature of a fuel is closely related to processes to achieve the desired volatility characteristics the molecular structure of its component hydrocarbons. and cetane number determines what the gravity will be. For example, the naphthenes tend to have low pour points FLASH POINT and relatively low cetane numbers, whereas the paraffins tend to have high pour points and relatively high cetane The flash point is the temperature to which the fuel must numbers. be heated to create a sufficient mixture of fuel vapor and air above the surface of the liquid so that ignition will Since low pour points often can be obtained only at the occur when the mixture is exposed to an open flame. expense of lower cetane number or higher volatility, the Various states and insurance companies have mandatory pour-point specification should not be any lower than requirements for flash point based on fire hazard, which necessary. must be taken into account when writing diesel-fuel CLOUD POINT specifications. Diesel fuel becomes cloudy and forms wax crystals and CARBON RESIDUE other solid substances at some temperature above the The tendency of a diesel fuel to form carbon deposits in pour point. The temperature at which clouding begins is an engine may be roughly approximated by determining called the cloud point. the carbon residue of the fuel. Carbon residue is the Since the wax crystals clog fuel filters and supply lines, amount of material left after evaporation and chemical and since this occurs at temperatures above the pour decomposition of the fuel has taken place at an elevated point, the cloud point may be even more important in a temperature for a specified period of time. High carbon fuel specification than the pour point. Like the pour point, residue values indicate the possibility of increased the cloud point depends on the hydrocarbon composition combustion chamber deposits and exhaust smoke. of the fuel. Although carbon-residue tests are fairly effective in Although cloud points seem to occur from 8° to 10°F (5° predicting deposit formation of base fuels, they are not to 6°C) above the pour points, cloud point as high as 15° good predictors when the fuels contain ignition improvers. or even 20°F (8° to 10°C) above the pour points are not Any specification for carbon residue should be stated for uncommon. the base fuel. VISCOSITY ASH Diesel engine injection pumps perform most effectively Small amounts of non-burnable material are found in diesel when the fuel has the proper “body” or viscosity. Lower fuel in the form of soluble metallic soaps and abrasive viscosity may require more frequent maintenance of solids. Since diesel engine injectors are precision-made injection systems parts. Viscosity also has some influence units of extremely close fits and tolerances, they are on the atomization of the fuel when it is injected. sensitive to any abrasive material in the fuel. If the viscosity is too high, excessively high pressures The ASTM method used to determine the amount of these can occur in the injection system. Therefore, the proper materials in a diesel fuel measures the ash content of viscosity or resistance to flow of diesel fuel becomes a the fuel. Burning a small sample of the fuel in a weighed prime requirement. container until all of the carbon matter has disappeared, as shown by the container and residue reaching a DENSITY AND GRAVITY constant weight, does this. The weight of the unburnable The gravity of diesel fuel is an index of its density or residue divided by the weight of the original fuel sample weight per unit volume (kg/L at 15°C). The denser the fuel, and multiplied by 100 is reported as the ash content of the higher its heat content. Since fuel is purchased on a fuel (percent by weight). volume basis, gravity is used in purchasing specifications Continued on next page KN52281,0000E89 -19-01JUN15-5/7 01-18 012716 PN=22 FUELS KNOCK IN DIESEL ENGINES In a spark-ignition engine where the fuel-air charge is mixed and then compressed before ignition takes place, knock is caused by the fuel burning TOO RAPIDLY. To control the rate of burning, tetraethyl lead is added. DXP05296 —UN—05MAY15 In diesel engines, knock is due to the fuel igniting TOO SLOWLY. It should start to burn almost as soon as it is injected (Fig. 12-C and Fig. 13-C). If there is much delay, a fuel buildup results, which burns with explosive force and causes knocking. Fuel charge ignites early and burns evenly to overcome knocking (proper burning)(Fig. 12-A.). Fig. 12 — Proper Burning Ignition of fuel charge is delayed followed by a small explosion (poor burning)(Fig. 12-B.). Good diesel fuel provides for early spontaneous combustion. By contrast, good gasoline fuels avoid spontaneous burning. DXP05405 —UN—06MAY15 RECOMMENDED DIESEL FUELS FOR FARM AND INDUSTRIAL MACHINES Type of Engine Service Ambient Air Diesel Fuel Temperature Grade No. Light load, lo

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