For 1990-2009 cars

Complaint/Condition | Possible Cause(s) | Correction(s)
--- | --- | ---
Low Oil Pressure or Fluctuating (Oil Light may be On or Flashing) | Improper viscosity engine oil. | Replace engine oil with correct viscosity.
Faulty gauge. | Verify oil pressure and check sending unit and gauge. (Refer to "Oil Pressure Check" in this section.)
High ambient temperature. | Check cooling system and verify correct engine oil viscosity.
Contaminated engine oil. | Verify engine oil is diluted with gasoline, coolant, etc.
Frozen water in oil pan. | Thaw water and change oil.
Cracked oil pickup tube and/or gallery plug. | Verify oil pickup tube is not cracked and all seals/plugs are not damaged and installed.
Faulty regulator valve. | Replace valve.
Faulty oil pump. | Replace oil pump.
Engine running clearances excessive. | Refer to the Basic Engine section and check bearing clearances.
Crankcase over/under filled. | Verify oil level and quantity in crankcase.
High Oil Pressure | Improper viscosity. | Replace engine oil with correct viscosity.
Faulty oil pressure gauge. | Verify oil pressure and check sending unit and gauge.
Plugged oil filter. | Replace oil filter.
Ambient temperatures to low. | Verify correct viscosity engine oil.
Faulty regulator valve. | Replace valve.
Oil Light On or Flashing | Low oil. | Add oil.
Coolant in Oil | Cylinder head plug or gasket. Cylinder head/block casting porosity. | Inspect cylinder head plug. Replace appropriate casting.