Pontiac 3100 engine oil usage?

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I have two 1995 Pontiac Grand Am's in the family that have 3.1 liter engines. They both started using oil at about 105,000 miles. Oil was always changed at 3000-3500 miles with maybe a quart used per change. Suddenly they both used 2-3 quarts and continue to use that much or more over each change.
Have not taken it to a dealer. I can't find where it is going. No drips on floor or oil under the car. No smoke at startup or while engine is idling or at cruise rpm.

Another person told me he has same problem.

Any suggestions?

posted by  rogerevilone

water in the oil, or vice versa?

posted by  asa67_stang

No water in oil, no oil in water. Just less oil in crankcase.

posted by  rogerevilone

how 'bout your plugs? how do they look?

it's gotta be goin somewhere, the oil-stealing fairies aren't taking it
when you had it at cruise RPM, was the engine hot? and even that won't be exactly the same as when you're driving

posted by  asa67_stang

Doing the math with the numbers you provide, you are using one quart or less of oil every 1k miles. This is considered well within normal usage. The fact that you are using more than you previously had can be chalked up to the fact that your engine isn't getting any newer.

If there are in fact no leaks, then the oil has to be going out the tail pipe. Again, if it's not enough to see it's probably not enough to be considered excessive use. The only way to answer your question definitively is to have the car checked out by a qualified technician.

posted by  vwhobo

I assume it is being burned and going out the tailpipe. I assume it is when the engine is warm because of the lack of smoke. What I don't understand is why did it start happening suddenly. Every oil change is normal, maybe down a quart and the next time it's down two quarts at 1-1.5k. And stays that way on each change. High milage oil and "Extend" seems to help but you need to check the oil every 500 mi. to feel safe. What could fail to cause the oil burning?

posted by  rogerevilone

Well you see, here's my problem. If it's going out the tailpipe, it would be smoking. Having the engine warm has no effect on the visibility of burning oil. However you said no smoke. It really can't be both. Someone needs to determine where the oil is going, and I don't have the ability to do so online, which takes us back to seeing a qualified tech.

posted by  vwhobo

I had this exact same problem on my 1995 Oldsmobile Cutlass Supreme with 3100 engine. It began to use more and more oil and suddenly began using more oil than gas. After much research, I finally replaced the intake manifold gasket and now it uses about 1/8th quart over 3,000 miles. The car has 165,000 miles on it. Burning as much oil as it did (about 1 quart every 200-500 miles) made a mess. It clogged the EGR port on the plenum which made the check engine light come on. After some work, it now runs good.

posted by  The Pretender

If it is definatly NOT leaking into the ground then have your coolant tested for oil in it. May be leaking in there....if not then its being burned. Check the plugs...if they dont seem to be fouled then get you a bumper sticker that says "ghost rider" and if one or two are fouled you might wanna have your heads rebuilt because your valves are leaking the oil into the cylenders...then again it could be a piston ring.

posted by  DodgeRida67

And of course, strong possiblity its a gasket.

posted by  DodgeRida67

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