VEHICLE MAINTENANCE AND MPG

GOAL:

To assist students in becoming wise energy consumers by understanding how to increase a vehicle's MPG by performing preventive maintenance.

OBJECTIVES:

The student will be able to:

1. Understand that vehicle maintenance can save fuel and money.

2. Identify maintenance items which affect MPG.

LESSON/INFORMATION:

Tires.

Tires are THE control of a vehicle. They are the means by which a vehicle is able steer, stop, and GO. This is commonly referred to as traction. Traction is a result of many factors. Among the many factors that effect traction, the most important are the weight applied to the tire and road, the condition of the road, the condition of the tire, and the amount of surface contact between the tire and the road. For a given size of tire, any increase or decrease in weight will result in a corresponding change in traction. As a road becomes more or less slippery, so does traction decrease or increase. Surface contact between the tire and the road is a factor of tire size and shape as well as tire inflation. Tires must not be either too large or too small for the vehicle; follow the manufacturer's recommendation for tire size. For a tire to have its maximum designed contact with the road it must not be either over or under inflated. An overinflated tire reduces the tire and road surface contact patch and causes the tire to wear excessively in the center area of the tread. See Figure 1 for a tire that has been run overinflated.

Figure 1

An underinflated tire also reduces the tire to road contact patch area and will wear the tire excessively on the edges of the tire. Additionally, underinflated tires tend to squirm, that is they wiggle from side to side instead of tracking in a straight line. It is the loss of contact patch and squirming that causes a loss in fuel economy. See Figure 2 for the typical tread wear due to underinflation.

Figure 2

As tires roll a certain amount of drag occurs. Due to alignment geometry, this drag tends to make the front tires of a rear wheel drive vehicle move in an outward fashion as the vehicle moves forward. A front wheel drive vehicle's tires tend to move in an inward fashion as the vehicle moves forward. As the tires move in this outward or inward fashion, tires experience greater amounts of drag and resistance increased tire wear rates and decreased fuel economy results. To counteract these effects, alignment geometry is statically adjusted toe-in or toe-out so that the vehicles tires roll in a straight, non-scuffing, and least resistant manner. Proper toe setting of the front wheels is very important to tire life as well as fuel economy. See Figure 3 for a tire which has been subjected to an improper toe setting. Vehicles equipped with independent rear suspensions require periodic alignment corrections; solid rear axles rarely lose their alignments.

Figure 3

Out-of-balance tires may also affect MPG. If a tire is unbalanced, the unbalanced dynamic forces causes the tire to run eccentrically. This eccentric movement causes reduced tire traction. The loss of traction results in a power loss, thus MPG is reduced. Additionally, unbalanced tires wear out faster. See Figure 4 for the effect on a tire that has been improperly balanced.

Figure 4

Figures 1-4 reprinted with permission from Glencoe Publishing Co.

Oil and Filter.

Correct selection, as well as appropriate and timely servicing of the engine's oil and filter may influence MPG. Manufacturer's owner's manuals list appropriate viscosity (weight), and grades of oil that provide protection against engine wear and deterioration. Typically, manufacturer's provide a chart illustrating the recommended viscosity as a function of vehicle load and ambient temperature. Figure 5A displays a typical manufacturer's recommended oil viscosity for any given temperature.

Figure 5A

In Figure 5B, this manufacturer recommends a multiple viscosity, 10 W 30 oil if the average ambient temperature is above 0 °F and below 100°F. If the average ambient temperature is out of this range a 5 W 30 oil must be selected. If the viscosity is too high for the ambient temperature, the oil pump will have to work too hard to deliver the oil and result in lower MPG. Conversely, if the oil viscosity is too low then the engine will have an excessive amount of internal friction; lower MPG will result.

Figure 5B

Both conditions -- too high a viscosity or too low a viscosity -- will result in excessive engine wear. Owner's manuals also describe the recommended American Petroleum Institute (API) oil ratings for that vehicle. An API SG or higher rating is typically recommended for late model gasoline engines. See Figure 6 for a typical oil container marking for an oil's grade. Failure to have an oil with the correct rating will effect higher engine wear or higher engine deposit levels; in time, either or both will reduce a vehicle's MPG.

Figure 6

A proper oil filter can influence a vehicle's MPG. Clogged, incorrectly applied, or substandard quality oil filters can reduce MPG. The manufacturer's owner's manual specifies the proper oil filter and change interval. It is important that oil filters are changed at regular intervals and meet manufacturer's specifications to protect vital engine parts and optimize oil pump performance. Failure to adhere to these recommendations will result in excessive engine wear and decreased MPG.

Tune Ups.

Most vehicle owners are aware that engine tune ups are the most significant maintenance item in preserving MPG. To the average vehicle owner, a tune up consists of replacing worn spark plugs and ignition parts such as the distributor cap and rotor or spark plug wires. While these are a very important part of an engine tune up, other items must be serviced, checked, adjusted, or replaced to optimize engine MPG. Owner's Manuals usually recommend: regular replacement of fuel, PCV, and air filters; periodically checking the operation and servicing of EGR, EGO, and PCV valves, ignition timing as well as other emissions control devices. See Figure 7 for a manufacturer's typical scheduled maintenance chart. Failure to properly service or replace all these items can result in significant MPG reductions. A properly tuned engine vs. an untuned engine can save 20% or more in fuel. Additionally, the tuned engine will start easier, run smoother, and last longer than the untuned engine.

Figure 7

LIGHT DUTY CYCLE - SCEDULE 1 (0 TO 60,000 miles)

SCHEDULED MAINTENANCE SERVICES FOR EMISSION CONTROL AND PROPER VEHICLE PERFORMANCE

Inspection and Service should also be performed anytime a malfunction is observed or suspected. Retain all receipts.

Service Code:

X - Sheduled maintenance for all vehicles

O - Sheduled mainteance for all except California vehicles. Recommended for proper vehile performance for vehicles built for sale in California.

EMISSION RELATED COMPONENT MAINTENANCE	SERVICE INTERVAL	MILAGE IN THOUSANDS KILOMETERS IN THOUSANDS	(1) (1)	7.5 12	15 24	22.5 35	30 45	37.5 60	45 72	52.5 84	60 96
DRIVE BELTS-INSPECT & ADJUST BELT TENSION; REPLACE AS NECESSARY			AT		O(2)		X		O(2)		O
EGR-VALVE AND TUBE - REPLACE; EGR PASSAGES CLEAN			AT								O(3)
ENGINE AIR FILTER - REPLACE			AT				X				O
IGNITION CABLES, DISTRIBUTOR CAP, & ROTOR - REPLACE			AT								O
OXYGEN SENSOR - REPLACE			AT
PCV VALVE - REPLACE			AT								O(3)
SPARK PLUGS - REPLACE			AT				X				O
VACUUM OPERATED EMISSION SYSTEM COMPONENTS - REPLACE (3)			AT								O

EMISSION RELATED COMPONENT MAINTENANCE	SERVICE INTERVAL	MILAGE IN THOUSANDS KILOMETERS IN THOUSANDS	(1) (1)	67.5 106	75 129	82.5 132	90 144	97.5 156	105 168	112.5 180	120 192
DRIVE BELTS-INSPECT & ADJUST BELT TENSION; REPLACE AS NECESSARY			AT		O		O		O		O
EGR-VALVE AND TUBE - REPLACE; EGR PASSAGES CLEAN			AT								O(3)
ENGINE AIR FILTER - REPLACE			AT				O				O
IGNITION CABLES, DISTRIBUTOR CAP, & ROTOR - REPLACE			AT								O
OXYGEN SENSOR - REPLACE			AT			O(3)
PCV VALVE - REPLACE			AT								O(3)
SPARK PLUGS - REPLACE			AT				O				O
VACUUM OPERATED EMISSION SYSTEM COMPONENTS - REPLACE (3)			AT								O

(1) Where both time and milage are shown, follow the interval which occurs first.

(2) For California vehicles, this maintenance is recommended by Chrysler to the owner but is not required to maintain the warranty on the air pump drive belt.

(3) If so equiped, these parts are to be replaced at the indicated milage or when the emissions maintenance reminder light remains on continuously with the key in the "on" position, whichever occurs first.

ACTIVITY:

Caution: Make sure to concentrate on driving and observe the posted speed limits. It is not a good idea to perform this analysis on a congested road.

1. Take a pressure reading on each tire while they are cold. Use the owner's manual to determine the correct pressure reading.

2. Drive vehicle at a steady speed on a smooth road to determine if the vehicle vibrates. Drive the vehicle at several different speeds, say 30, 40, 50, and 60 miles per hour.

3. Drive vehicle on a straight, smooth, level road to determine alignment conditions. While still keeping control of the steering wheel, slightly release the normal grip on the steering wheel. The vehicle should not exhibit any appreciable directional pull or lead to either the left or the right.

4. From owner, determine last oil, filter and tune-up. From the owner's manual, determine the correct change interval for both the oil and the filter. Determine the correct viscosity for the anticipated ambient temperature.

5. Determine Base MPG for three tanks of fuel. See the MPG activity for the correct procedures.

6. Make any corrections found in steps 1 through 4. These may be done one at a time. It is permissible to make all the changes and corrections at the same time.

7. Repeat the three tank MPG test.

8. Compare the MPG before and after the changes and corrections.

9. Calculate percent fuel saved.

10. Using $1.30 per gallon, calculate the projected annual gallons and dollars used for 10,000 miles of driving before and after the adjustments and repairs.

11. Compare cost of repairs vs. cost savings.

CONCLUSIONS:

1. Compare the before and after cost for operating this vehicle.

2. How many gallons of fuel could be saved in 10,000 miles?

3. What are the annual cost savings?

4. What would the cost savings be if fuel cost $2.00 per gallon? $2.50 per gallon?

INFORMATION CHECK

Place a "T" before the statements that are true and an "F" before the statements that are false. After each false statement, explain why it is false.

_______1. Traction only affects braking.

_______2. Proper selection of oil and filters can make a difference in MPG.

_______3. A tire which has been run low on air for some time will show signs of wear in the center treads.

_______4. All modern engines need to have 10 W 30 oil.

_______5. Regular tune ups can sustain a vehicle's MPG; spark plugs and spark plug wires are the only parts that need regular servicing.

_______6. Air and fuel filters require periodic replacing to ensure optimum MPG.

_______7. Proper toe adjustment is most important to tire life and can seriously effect MPG.

_______8. Emissions control devices such as the PCV and EGO valves need to be serviced when they fail.

_______9. Proper tire inflation can add miles to tire life as well as minimize energy losses due to tire squirm.

_______10. The owner's manual is a good source for preventive maintenance that can keep a vehicle capable of delivering its top fuel mileage.

TEACHER'S NOTES

Students should thoroughly read the background information before beginning the activity. Encourage the students to familiarize themselves with the owner's manual for their automobile. Many people never read the book supplied by the manufacturer. There is an abundance of valuable fuel saving information in this book. Most fuel saving ideas will also extend the useful, trouble-free life of the vehicle. Maintenance habits and techniques are usually inherited from the person who teaches us how to drive or who has had the greatest influence on our attitude towards driving. Unfortunately, many people truly believe that:

"if it ain't broke, don't fix it"
or
"don't maintain anything; when it breaks, get rid of it. You'll be dollars ahead!"

Most average people cannot afford the replace their vehicles every three or four years. The average new vehicle costs well over $12,000.00.

It may be interesting to get several in the class to discuss how reading their owner's book and performing necessary maintenance has saved or is projected to save fuel dollars. Getting students to share their successes with such activities can stimulate a desire to explore other ways that learning may impact their lives.

Answers to Information Check Questions:

1. False. Traction effects braking, steering, and the ability to go.

3. False. Tires that are run low of air will wear more on the edges; heavy center tread wear is a result of over inflation.

4. False. Many modern engines require 10 W 30 oil in moderate temperatures; however, there is no ONE best oil viscosity for Louisiana. For some vehicles, winter temperatures in the northern Louisiana sector may mandate a 5 W 30 oil while statewide summer temperatures may mandate a 10 W 40 oil.

5. False. Spark plugs and spark plug wires are important to tune ups, but servicing, timing, and emissions control devices are also an important part of an engine tune up.

8. False. Emissions control devices need regular servicing; when improperly operating, these items cause excessive fuel consumption, make the vehicle run rough, and cause excessive air pollution.

Recommended Reading:

Abbott, Sheldon L. and Ivan D. Hineman. Automotive Suspension and Steering, 2nd ed. Mission Hills, California, 1982, Glencoe Publishing Co.

Ellinger, Herbert E.. Automechanics, 4th. ed. Englewood Cliffs, New Jersey, 1988, Prentice Hall, Inc.

New York Energy Education Project, Research Foundation of the State University of New York. Albany, N.Y. 1985

Tune Up Today - $ave Tomorrow. Louisiana Department of Natural Resources, Baton Rouge, LA, n.d.

General Motors Corporation. 1990 Chevrolet C/K Series Truck Owner's Manual. Part No. C-9004 B, n.d.

Chrysler Motors. 1990 Dodge Dakota Owner's Manual. 81-326-0032, n.d.

Comments or questions to: TechAsmt@LA.GOV

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