The headgaskets/valve cover gaskets were changed along with a minor valve adjustment in Feb of this year. After that, the oil pressure warning light was blinking on/off and it needed 2 qts of oil. I added the oil and brought it back to the repair shop where they checked everything, didn't find anything wrong, but changed the oil pressure sensor and added some oil. The oil pressure light stopped coming ON. A week later I checked the oil and it was low (-1 qt) which I added. On anytime cold start, when oil level is normal, a trail of white smoke folows until the engine temp gauge is at midline temp. The oil used is 10W/40 due to high mileage. Took it two more times to two other repair shops and Auto Zone for electronics check-up pertaining to this issue and to replace the oil pressure sensor if needed. Everytime it showed that everything is OK. Regular maintenance is done on schedule and proper oil level is maintained, but on monthly occassions I've had to add oil (ranging from 0.5 - 1.5 qts) and again the same problem comes: white smoke out of the tail pipe on cold start at anytime of day, any weather condition, the engine pressure oil light does not come on and engine scan shows OK. Can you please give some advise on this very anoying issue? The car runs great without any other major or minor problems. I love this car and intend to restore it in a very near future and keep it forever, but what can I do?
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1993 Mitsubishi Expo Question: Oil Pressure Warning Light Off but engine needs oil
Answer #1patrick mannion from Greg Solow's Engine Room, December 04, 2009, 11:10Master
An engine that is burning oil emits blue colored smoke that has an oder of burning oil. It is heavy blue to blue gray in color. If the engine has worn valve guides or valve guide seals oil may drip into the cylinders when the engine is turned off and allowed to cool, then when you start the engine up in the morning you get that trail of smoke out the exhaust. light colored smoke out the exhaust is normal until the engine warms up, especially noticeable on cold mornings dense air. White or sweet smelling smoke out the exhaust perhaps accompanied by rough running would be a sign of a blown head gasket.
Some oil consumption on a higher mileage engine is normal, Mercedes used to say 1 quart per 1000 miles before they would do anything under warentee, (which I feel is excessive).
If your car badly over heated and that was the cause of the head gasket failure, the overheating episode could have damaged the piston oil control rings and oil is now not being "scapped off" the cylinder walls by the oil control rings.
I would let the car cool down, start from cold allow to run fro a few minutes, remove the spark plugs see if they have oil fouling (not carbon fouling due to rich fuel mixture on cold start up). Then I would drive the car and get it up to operating temperature and do a cylinder leakage check. This checks the condition of the rings but cannot access the exact condition of each ring (either oil control or piston compression rings) it just gives you an indication of blow by past each piston.
Perhaps replace the PCV valve it is cheap and easy to fit. Does your car have any engine oil leaks and check the tailpipe for signs of oily deposits in the pipe itself.
I am afraid the route of your problem may still be internal in the engine.