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Fuel cost is the largest single expense over the life of anengine.
Unfortunately, often as fuel costs increase, the quality of available fueldecreases. It is important to understand the effects an inferior fuel qualitycan have on your engine.
Unless the specific measures mentioned in this book are taken, using theincorrect fuel can result in excessive engine wear and perhaps even prematureengine failure.
Fuel Costs Versus Operating Costs
Before 1970, most manufacturers of medium to high speed diesel enginesdesigned them to operate on fuels that were highly refined("distillate" fuels). Efficient, economical operation of these enginesdepended on the quality of fuel they burned and there was a readily availablesupply of inexpensive, fair quality fuel. Fuel costs were not considered asignificant factor before the early 1970s.
A major oil supply crisis occurred in 1973. It created an overnight shortageof fuels around the world. Prices rose very sharply, and have remained higherthan anyone would have predicted. The quality of available fuels correspondinglydecreased and is expected to decrease further. Today owners are acutely aware offuel expense and how it affects their operation.
Graph showing crude oil barrel costs over the past several years(Diesel fuel
prices have a similar trend since diesel fuels are refined from crude oil.)
Before the 1973 oil crisis, fuel typically represented less than 30% of theoperating expense of an engine. Today this percentage is often 60 to 90%. Manyowners of large engines are seriously considering alternative fuels to helpreduce escalating fuel costs. This booklet discusses some alternatives and listssome of the most critical characteristics of fuel so you can buy fuelintelligently.
This booklet does not contain information on how to operate enginesfor maximum fuel economy. Such information is available in other publications.Refer also to Form LEKQ4487, Engine Data Sheet 60.2, "Fuel ConservationPractices".
Understanding Fuel
Fuel produces power in a diesel engine when it is atomized and mixed with air inthe combustion chamber. Pressure caused by the piston rising in the cylindercauses a rapid temperature increase. When fuel is injected, the fuel/air mixtureignites and the energy of the fuel is released to force the pistons downward andturn the crankshaft. A perfect fuel would burn completely, leaving no residue orsmoke products. However, there is no perfect fuel.
Ignition/Power Stroke. Injected diesel fuel and
compressed air ignite from the rapid rise in heat.
Get the Facts on Fuel
Price is not the only factor when considering the fuel for your engine.Before you make a decision on what type of fuel to burn, read this book. It hasbasic, easy-to-understand explanations of the functions and properties of fueland how they affect your engine.
Once you understand the differences between fuels, it will be easier for youto see the consequences of using an incorrect or poor fuel.
This book is an overview of basic fuel information. Refer to the publicationslist at the end, for a listing of publications providing more details onparticular items.
Remember - clean fuel meeting Caterpillar's fuel recommendations will giveyou normal engine service life and performance; anything less is a compromise.
Fuel Selection
Experience has proven that distillate fuels meeting basic specifications willresult in optimum engine performance and durability. Depending on fuel costs andavailability, proper application of alternative fuels such as: crude oil;blended; or residual fuel can also provide a cost competitive engine operation.Before discussing these fuels we need to define fuel properties and their effecton engine operation and fuel handling systems.
Fuel Properties Listed by Their Functional Effects
Fuel quality can significantly affect the performance and maintenance of anydiesel engine. It is important to understand basic fuel properties to be able tojudge fuel quality. The following properties have an impact on the operation ofa diesel engine and its fuel handling and fuel treatment systems.
For more specific information, refer to Engine Data Sheet 62.0, FormLEKQ3255.
Fuel quality is not visually apparent. All or none of thesesamples may be
"good" fuels.
Specific Gravity
The specific gravity of diesel fuel is the weight of a fixed volume of fuelcompared to the weight of the same volume of water (at the same temperature).The higher the specific gravity, the heavier the fuel. Heavier fuels have moreenergy or power (per volume) for the engine to use.
Specific gravity can be measured with a special fuel hydrometer. The readingon the hydrometer is an American Petroleum Institute (API) scale. The scale isinverse to the specific gravity. That is, the higher the API number, the lighterthe fuel. For most Caterpillar diesel engines an API reading of 35 would beoptimum. Lighter fuels like kerosene might have a measurement of 40- 44 API.
1P7438 Beaker, 1P7408 Thermo-Hydrometer (29 to 41 API)5P2712
Thermo-Hydrometer (39 to 51 API).
The hydrometer floats in the fuel. You can note the point at which the liquidlevel intersects the hydrometer scale and read the API fuel gravity.
The hydrometer reading is affected by the temperature of the fuel. Always usethe correction table included with the tool to compensate for actual fueltemperature. Detailed instructions are given in Tool Operating Manual,"9U7840 Fuel Injection Equipment Calibration Fluid Test Kit", Form No.NEHSO607-01.
Engine Effects
Light Fuels:
Lighter fuels like kerosene will not produce rated power. (Specificationsheets usually show ratings when using fuel having 35 API density, at 29?C[85?F], weighing 7.001 pounds per gallon, and having 18,390 BTU's per pound.The same fuel of 35 API density weighs 7.076 pounds per gallon at 15?C[60?F].) When comparing fuel consumption or engine performance, always know thetemperature of the fuel measurement for correct gravity and density.
Engine fuel settings should not be adjusted to compensate for a power losswith lighter fuels (with a density number higher than 35 API). Fuel systemcomponent life can be decreased with very light fuels because lubrication willbe less effective (due to low viscosity).
Lighter fuels may also be a blend of ethanol or methanol with diesel fuel.Blending of alcohol (ethanol or methanol) or gasoline into a diesel fuel willcreate an explosive atmosphere in the fuel tank. In addition, water condensationin the tank can cause the alcohol to separate and stratify in the tank.Caterpillar recommends against such blends.
Heavy Fuels:
A heavy fuel tends to create more combustion chamber deposit formationswhich can cause abnormal cylinder liner and ring wear. This problein is mostnoticeable in smaller, high speed engines. See the section "Blended [Heavy]Fuels" on Page 31.
Steps to Correct Specific Gravity:
Blending is