Preliminary

1. The causes of excessive oil consumption may include the following conditions.

•	External oil leaks--Refer to General Engine Diagnosis.

•	Incorrect oil level or reading of the oil level indicator. With the vehicle on a level surface, run the engine for a few minutes, allow adequate drain down time (2-3 minutes) and check for the correct engine oil level.

•	Incorrect oil viscosity--Refer to the vehicle Owners Manual and use the recommended SAE grade and viscosity for the operating environment.

•	Continuous high speed driving and/or severe usage

•	Crankcase ventilation system restriction or malfunction

•	Worn valve guides and/or valve stems

•	Worn, or incorrectly installed valve stem oil seals

•	Broken, worn or incorrectly seated piston rings--Allow adequate time for the rings to seat. Replace worn pistons rings as necessary.

•	Piston and rings incorrectly installed or incorrectly fitted to the cylinder bore

•	Excessive piston to bore clearance

2. Perform a cylinder compression test. Refer to Engine Compression Test.
3. If the compression test indicates a worn valve train, inspect for the following:

•	Worn valve guides

•	Worn valve stems

•	Worn or burnt valves or valve seats

•	Worn, brittle, or incorrectly installed valve stem oil seals

4. If the compression test indicates worn or damaged piston rings, inspect the following:

•	Broken or incorrectly seated piston rings

•	Excessive piston ring end gap

•	Excessive cylinder bore wear or taper

•	Cylinder damage

•	Piston damage