Oil Consumption Test

The following diagnostic procedure is intended to be used to determine the source of excessive internal oil consumption.
1. Determine what is considered excessive oil consumption, i.e., how many miles are driven per quart of oil? Also, Determine owner's driving habits, i.e., sustained high speed operation, towing, extended idle, etc.

Oil usage is normally greater during the first 16,000 kilometers (10,000 miles) of service. As mileage increases, oil usage generally decreases. Vehicles in normal service should get at least 1450 km (900 miles) per quart after 16,000 kilometers (10,000 miles) of service. High speed driving, towing, high ambient temperature etc. may result in greater oil usage.

2. Verify engine has no external oil leak.
3. Verify engine has the correct oil level dipstick.
4. Verify that the engine is NOT being run in an overfilled condition. Check the oil level at least 5 minutes after a hot shutdown with the vehicle parked on a level surface. In no case should the level be above the "F" mark on the oil level dipstick. If a significant overfill is indicated, perform steps 5a through 5d.
5. Perform an oil consumption test:
a. Drain the engine oil, replace the oil filter, and refill with one quart less than the recommended amount of oil.
b. Run the engine for 3 minutes (10 minutes if cold), then allow oil to drain to oil pan for at least 5 minutes (vehicle on level surface).
c. Remove oil level dipstick and wipe clean. (Do not wipe with anything contaminated with silicone compounds.) Install the oil level dipstick being sure to seat the oil level dipstick firmly in the oil level indicator tube. Remove the oil level dipstick and scribe a mark on the back (unmarked) surface at the indicated oil level. (This level should be about the same as the "L" mark on the face of the oil level dipstick.)
d. Add one quart of oil. Start the engine and allow to idle for at least two minutes. Shut off the engine and allow oil to drain to oil pan for at least 5 minutes. Mark the oil level dipstick using the procedure above. (This level may be slightly below the "F" mark.)
e. Record the vehicle's mileage.
f. Instruct the owner to drive the vehicle as usual and:
1. Check the oil level regularly at intervals of 100 to 150 miles.
2. Return to the service location when the oil level drops below the "L" mark on the oil level dipstick.
3. In an emergency, add only full quarts of the same oil and note the mileage at which the oil is added.
9. Check the oil level under the same conditions and at the same location as in steps c and d above.
1. Measure the distance from the oil level to the UPPER scribe mark on the oil level dipstick and record.
2. Measure the distance between the two scribe marks and record.
3. Divide the first measurement by the second.
4. Divide the distance driven during the oil test by the result. This quantity is the approximate oil consumption rate in Miles Per Quart (MPQ).
h. If the oil consumption rate determined is unacceptable, proceed to step 6.
6. Check Positive Crankcase Ventilation (PCV) valve system. Make sure system is not plugged.
7. Check for plugged oil drain back holes in the cylinder heads and the cylinder block.
8. If, after performing the above, the condition still exists, proceed to step
9. Perform the compression test.
10. Worn or damaged internal engine components can cause excessive oil consumption. Small deposits of oil on the tip of the spark plugs can be a clue to internal oil consumption. If internal oil consumption still persists, proceed as follows:
a. Remove the engine from the vehicle and place it on an engine work stand. Remove intake manifolds, cylinder heads, oil pan, and oil pump.
b. Check piston ring clearance, ring gap and ring orientation. Service as required.
c. Check for excessive bearing clearance. Service as required.

NOTE: After checking for worn parts, if it is determined parts should be replaced, make sure correct replacement parts are used.

11. Repeat the tests to verify that the concern has been corrected.