DRIVELINE LUBRICANTS:
A POSSIBLE LOSS OF FUEL MILEAGE

GOALS:

To assist students in understanding the relationship between excessive axle lubricant viscosity and optimum fuel economy.

OBJECTIVES:

The student will understand how proper driveline lubricant viscosity:

1. Increases driveline performance.

2. Affects fuel economy.

LESSON / INFORMATION:

Driveline components, transmissions, power dividers, auxiliary transmissions, and differentials, require lubricants that can sustain forces generated by gears. If the lubricant is squeezed from the gears, higher than normal friction, loss of energy, and increased wear results. To overcome this problem, 85W or 125W hypoid oils with EP (Extreme Pressure) additives have traditionally been used for gear trains. EP additives are special lubricant modifiers that help resist the squeezing force generated by gears.

Many new driveline components use lower viscosity, mineral based oils with anti-wear and EP agents or synthetic based EP additive lubricants. If the component is designed for these types of lubricants, energy savings result since the viscosity is lower. Heavy viscosity lubricants cause energy losses. Some technicians do not believe that the light weight oils can protect heavy duty components. When replacing or adding lubricants, they frequently use the traditional 85W or 125W EP lubricants.

Many newly designed components are closer tolerance and tighter fitting; therefore, the heavy viscosity oils will not flow between some moving components. This results in excessive premature wear and energy loss.

Decreased driveline component tolerance improves component life and increases fuel economy since a lower viscosity oil is recommended; thus, technicians must use the proper lubricants for each driveline component to ensure minimum wear and optimal fuel economy. Manufacturer's operators manuals, service manuals, or lubrication guides are the best sources for proper lubrication procedures of a specific year, make, and model vehicle.

ACTIVITY:

Complete the data chart below for at least three late model vehicles. Be sure at least one has been built within the last two years. Obtain the data from the owner's manual, manufacturer's manual, or a reliable technical reference manual. Once this data is collected, write a short report on the various driveline lubricants necessary for a repair shop to use in various makes, models, and types.

Vehicle #1	Transmission Type:	Transmission Model	Recommended Lubricant	Differential Type	Differential Model	Recommended Lubricant
Year:___________ Make:__________ Model:_________
Vehicle #2	Transmission Type:	Transmission Model	Recommended Lubricant	Differential Type	Differential Model	Recommended Lubricant
Year:___________ Make:__________ Model:_________
Vehicle #3	Transmission Type:	Transmission Model	Recommended Lubricant	Differential Type	Differential Model	Recommended Lubricant
Year:___________ Make:__________ Model:_________
Vehicle #4	Transmission Type:	Transmission Model	Recommended Lubricant	Differential Type	Differential Model	Recommended Lubricant
Year:___________ Make:__________ Model:_________

Summary:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

INFORMATION CHECK

Directions: Indicate whether the following statements are true or false. If the statement is false, explain why it is false.

1._________ Only hypoid axle oils have an EP agent.

2._________ Low viscosity, energy saving driveline lubricants may be used in all heavy vehicle drivelines.

3._________ EP agents prevent metal to metal contact as a result of the forces generated by the gears.

4._________ Lightweight, low viscosity driveline lubricants can reduce gear friction, thus conserving fuel.

TEACHER'S NOTES:

Over the last decade, driveline manufacturers have changed their lubricant requirements to correspond to the newer, close tolerance gear systems. These systems must use the proper lubricant. Heavy lubricants may seem more protective to components, but in truth, if heavy viscosity hypoid lubricants are improperly applied, not only will energy be lost, but gears, bearings, and shafts may be permanently damaged.

ANSWERS TO INFORMATION CHECK:

1. False. All driveline lubricants use some type of EP agent.

2. False. Only those systems designed for the low viscosity lubricants should use these.

3. True.

4. True.

REFERENCES:

Eaton Corporation. Eaton Truck Components: Synthetic Lubricants Benefits, Drive Axle Lubrication Requirements, Transmission Lubrications Lubricants. Bulletin TC-019-R1. 1992.

Mobil Product Data Sheet. Mobil 1© Synthetic Lubricants: PDSA-16, PDSA-18, PDSA-21, PDSA-23, PDSA-24, PDSA-26. 1991.

Comments or questions to: TechAsmt@LA.GOV

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