DIESEL FUEL
GRADE AND MPG

GOAL:

To understand that all diesel fuels are not the same.

OBJECTIVES:

The student will:

1. Learn to properly identify the different types of diesel fuel.

2. Learn how each fuel can affect MPG.

3. Learn how to select diesel fuel by anticipated weather conditions.

LESSON / INFORMATION:

Diesel fuels are classified 1D, 2D, and 4D. Low speed, stationary units use 4D fuels. 4D fuel is not appropriate for most mobile equipment. On-highway and mobile equipment use 1D and 2D fuels. High speed diesel engines use either 1D or 2D fuels. Important characteristics of diesel fuels are its viscosity, pour point, and cetane number. The primary differences between 1D and 2D fuel are the pour point and the viscosity. Pour point is the lowest temperature at which a liquid will flow. Viscosity is the resistance of a liquid to flow. A 1D fuel is designed for cold weather operation; thus, it is less viscous and has a lower pour point. A 2D fuel is used in warmer weather because it has a higher viscosity and pour point. The higher viscosity provides better lubrication qualities for the moving parts of the fuel injection system. Because 2D fuels contain more Btu's (British thermal units - the amount of heat necessary to raise one (1) pound of water one (1) degree fahrenheit) per gallon, they are able to deliver more power per gallon. This is critical to diesel engine fuel economy. The higher the Btu rating a diesel fuel has, the greater power yield per gallon; thus, higher mpg will result. Cetane rating is the diesel equivalent to gasoline's octane rating. Unlike an octane rating, which rates gasoline's resistance to spontaneous ignition, the cetane rating number (usually 40 to 55 for medium to high speed engines) notes the relative ease with which diesel fuel ignites. The higher the cetane number, the easier the fuel ignites; the higher the octane number, the more resistant the fuel is to ignition. Each manufacturer usually specifies a minimum or maximum cetane rating and the suggested operating temperature for 1D and 2D fuels. A given fuel may meet 1D or 2D specifications, but if the Btu rating is too low, then decreased fuel mpg will result.

ACTIVITY:

Locate a source for technical fuel data for two or more diesel powered vehicles such as an owner's manual, manufacturer's shop manual, or a manufacturer's maintenance manual. From one of these sources, determine the recommended operating temperature for 1D and 2D fuels. Enter the data on the chart of the Student Diesel Fuel Activity Sheet provided. From the source, determine the suggested cetane and Btu rating. Enter this data. Call or visit two or more local fuel distributors or a fueling station that sells large quantities of diesel fuel. From each fuel distributor or fuel station determine:

1. 1D and 2D cetane rating; and

2. 1D and 2D Btu rating; and

3. 1D and 2D cost per gallon.

STUDENT ACTIVITY SHEET:

Student Name:_________________________________

Date Activity Completed:___________

Purpose:

To compare 1D and 2D fuels for cost and potential for fuel economy.

Procedure:

1. Locate two or more diesel powered trucks.

2. Locate a technical source (owner's manual, shop manual or maintenance manual.)

3. From the source, determine the cetane and Btu requirements.

4. From fuel supplier (distributor or retailer), determine cetane, Btu, and cost per gallon of 1D and 2D fuels.

5. Complete chart data and compare.

6. From the data collected, determine which fuel should deliver the best mpg for each truck studied. Give (a) reason(s) why.

#1 Truck:

Make / Model:__________________________

Engine Type / Size:___________________

Recommended Fuel:

1D Temperature range ______°F to ______°F

2D Temperature range ______°F to ______°F

Recommended Cetane Rating:____________ (minimum) to _____________ (maximum)

Recommended Btu Range: _______________________ to __________________________

Make / Model:__________________________

Engine Type / Size:___________________

Recommended Fuel:

1D Temperature range ______°F to ______°F

2D Temperature range ______°F to ______°F

Recommended Cetane Rating:____________ (minimum) to _____________ (maximum)

Recommended Btu Range: _______________________ to __________________________

1D				2D
	Cetane Rating	BTU Rating	$/Gallon	Cetane Rating	BTU Rating	$/Gallon
Fuel Supplier #1
Fuel Supplier #2
Fuel Supplier #3

Which fuel should deliver the best mpg . . .

for Truck #1:______________________________?

for Truck #2:______________________________?

Why:__________________________________________

______________________________________________

______________________________________________

______________________________________________

INFORMATION CHECK

Indicate whether the statements below are true or false. If false, please correct to make it a true statement.

1._______ A fuel's viscosity is the same as a fuel's pour point.

2._______ A diesel fuel with a lower Btu rating will deliver more mpg.

3._______ 1D fuels are used when the temperatures are colder.

4._______ All diesel powered engines use the same type fuels.

5. Which of these are not a rating for diesel fuel:

A). Octane

B). Pour Point

C). Btu

D). 1D, 2D, or 4D

TEACHER'S NOTES

Many diesel operators in the deep south do not realize that 1D fuel is a winter graded fuel to improve cold weather starting and reduce fuel gelling during cold weather. Most do not realize that 1D fuels have a lower Btu rating; thus, mpg will drop with their usage. Even many 2D fuels have varying cetane and Btu values; thus, mpg will vary. To get the data for this student exercise, some persistence will be necessary. Most local fuel stations will not have or won't be able to supply the technical information requested. Students will need your assistance to locate a cooperative fuel distributor. A large retailer, such as a truck stop, might have access to the data.

Students may need a definition of a Btu. Simply put, a Btu is the amount of potential heat a given quantity of fuel can deliver. The classic physics definition is used, but may not be readily relevant to most students.

ANSWERS TO INFORMATION CHECK:

1. False. Although many people confuse viscosity with pour point, these are two independent attributes of a liquid. Each may be controlled independently in the refining process.

2. False. The higher the Btu value the more mpg the engine can deliver. This is provided the maximum Btu rating for that engine is not exceeded. A fuel with an excessively high Btu rating could damage a diesel engine. The engine will not yield the power from the excessive Btus, therefore no increased mpg will be realized.

3. True.

4. False. 1D and 2D fuels are for high speed diesel engines; 4D fuels are for low speed diesel engines.

5. A - Octane is a gasoline rating.

RECOMMENDED READING:

Diesel Engine Repair, pages 209 and 210

Automotive Fuels, pages 44-50

REFERENCES:

Diesel Engine Repair, John Wiley and Sons, Inc., New York, 1982.

Schatt, Robert. Automotive Fuels, Delmar Publications, Inc. Albany, NY. 1989.

Comments or questions to: TechAsmt@LA.GOV

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