Test

The following diagnostic procedure is used to determine the source of excessive internal oil consumption:

1. Define excessive oil consumption, such as the number of miles driven per liter (quart) of oil used. Also determine customer driving habits, such as sustained high speed operation, towing, extended idle, and other considerations.

NOTE: Oil use is normally greater during the first 16,100 km (10,000 miles) of service. As mileage increases, oil use generally decreases. Vehicles in normal service should get at least 1450 km (900 miles) per liter (quart) after 16,100 km (10,000 miles) of service. High speed driving, towing, high ambient temperature, and other factors may result in greater oil use.

2. Verify that the engine has no external oil leaks.
3. Verify that 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 five minutes after a hot shutdown with the vehicle parked on a level surface. In no case should the level be above the top of the "MAX" line on the dipstick. If significantly overfilled, perform steps 5a through 5d.
5. Perform an Oil Consumption Test:
a. Drain the engine oil, remove the oil bypass filter, and refill with one liter (quart) less than the recommended amount.
b. Run the engine for three minutes (10 minutes if cold) and allow the oil to drain back for at least five minutes with the vehicle on a level surface.
c. Remove the oil level dipstick and wipe it clean. (Do not wipe with anything contaminated with silicone compounds.) Reinstall 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 draw a mark on the back (unmarked) surface at the indicated oil level. (This level should be about the same as the ADD mark on the face of the oil level dipstick.)
d. Add one liter (quart) of oil. Restart the engine and allow it to idle for at least two minutes. Shut off the engine and allow the oil to drain back for at least five minutes. Mark the oil level dipstick, using the procedure above. The level may range from the "MAX" line to 10-13 mm below the "MAX" line. Repeat steps 5a and 5d if significantly over the "MAX" line.
e. Record the vehicle's mileage.
f. Instruct the customer to drive the vehicle as usual and:
(1) Check the oil level regularly at intervals of 160 to 240 km (100-150 miles).
(2) Return to the service point when the oil level drops below the lower (ADD) mark on the oil level dipstick.
(3) Add only full liters (quarts) of the same oil in an emergency. Note the mileage at which the oil is added.
f. Check the oil level under the same conditions and at the same location as in Steps c and d.
(1) Measure the distance from the oil level to the UPPER 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 kilometers per liter or in miles per quart.

h. If the oil consumption rate is unacceptable, go to Step 6.

6. Check the positive crankcase ventilation (PCV) system. Make sure the system is not plugged.
7. Check for plugged oil drain-back holes in the cylinder heads and the cylinder block.
8. If the condition still exists after performing the above tests, go to Step 9.
9. Perform a Cylinder Compression Test and/or perform a Cylinder Leak Detection Test with Engine Cylinder Leak Detection/Air Pressurization Kit. This can help determine the source of oil consumption such as valves, piston rings, or other areas.
10. Check the valve guides for excessive guide clearance. REPLACE all the valve stem seals after verifying the valve guide clearance.

NOTE: After determining if worn parts should be replaced, make sure correct replacement parts are used.

11. 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 the intake manifolds, cylinder heads, oil pan, and oil pump.
b. Check the piston ring clearance, ring gap, and ring orientation. Repair as required.
c. Check for excessive bearing clearance. Repair as required.

12. Perform Oil Consumption Test to confirm that the oil consumption concern has been resolved.