Oil Consumption Test

The following diagnostic procedure is intended to be used to determine the source of excessive internal oil consumption.

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 kilometers (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.

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 (e.g., sustained high speed operation, towing, extended idle, etc.).
2. Verify the engine has no external oil leaks.
3. Verify the 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. If a significant overfill is indicated, perform steps 5a through 5d.
5. Perform an oil consumption test:
a. Drain engine oil, replace the filter, and refill with one quart less than oil capacity.
b. Run the engine for 3 minutes (10 minutes if cold), then allow oil to drain to the oil pan for at least 5 minutes (vehicle on a level surface).
c. Remove the oil level dipstick and wipe it clean. (Do not wipe the indicator 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 the oil to drain to the 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 161 to 240 km (100 to 150 miles).
(2) Return 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.
g. Check the oil level under the same conditions and at the same location as in steps 5c and 5d.
(1) Measure the distance from the observed 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 kilometer per liter (KPL) or miles per quart (MPQ).
h. If the oil consumption rate determined is unacceptable, proceed to step 6.
6. Check the positive crankcase ventilation (PCV) valve system. Make sure the system is not plugged.
7. Check for plugged oil drain-back holes in the cylinder heads and cylinder block.
8. If, after performing the above, the condition still exists, proceed to step 9.
9. Perform a Compression Test, and/or perform a Cylinder Leakage Detector Test. This can be helpful in determining the source of oil consumption (e.g., valves, piston rings, etc.).
10. Worn or damaged internal engine components can cause excessive oil consumption. Small deposits of oil on the tips of 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 the intake manifolds, cylinder heads, oil pan, and oil pump.
b. Check piston ring clearance, piston ring gap and piston ring orientation. Service as required.
c. Check for excessive bearing clearance. Service as required.
11. Repeat test to verify concern has been repaired.

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