Why does my 23 year old engine burn oil?

[I<3flippyheadlights]

Well with all this talk of boost, thinking of boost, hearing about boost I now want to boost! But I need to solve some problems with the engine first before I start throwing more at it. Most importantly the burning oil issue. Its burns pretty consistently if I push the car. (guessing when I go above 4500 rpms) If I putz around town shifting below 4000 rpms I lose very little oil, when I go hard it is noticeable. :| How noticeable? How about a quarter to half a quart after 30 mins to a hour of fun driving. That is sort of a guess, but we need something to work with.

So last night I did a compression test on the car and got 180 across the board. Pretty good for the ol' gal. :8): This leads me to being more confused. I thought my oil rings were bad. With good compression, doesn't that mean the oil rings are good? I looked at the spark plugs which were fairly new (replaced them when I put in a new valve cover gasket) but they still had a bit of oil on the threads and the tips were black. Hope that helps and I wish I taken pictures. :fp::fp::fp:

Does anyone have any ideas? Thanks for the help guys. :mrgreen:

[Demon I Am]

How does the outside of your engine look? Maybe you have a really leaky Front/rear/oil pan gasket?

[vote4pedro]

check back by the cam angle sensor too, prone to leaks there. Also the rear main seal, which is a PITA to change.

[I<3flippyheadlights]

All the seals have been changed. My rear main does leak, but not enough to constitute the amount I'm losing. My engine bay is pretty clean.

[kung fu jesus]

A leak down test will be a more accurate assessmemt of where the oil is getting in.

You have to listen where thhe air is leaking out.

[Demon I Am]

How does the exhaust tip look? Are you blowing-out oil. Compression numbers look pretty decent though.

I'm losing about 1.5 qts per 1500 miles.

[I<3flippyheadlights]

Well I run rich and get a backfire every time I shift above 4200 rpms. When I red line it, people see some smoke coming out. (Black and white)

[I<3flippyheadlights]

A leak down test will be a more accurate assessmemt of where the oil is getting in.

You have to listen where thhe air is leaking out.

Exaplin how a leak down works and how do I hear the air leaking?

[kung fu jesus]

It's performed with an attachment you connect to an air compressor. It has a pair of gauges on it.

You remove all the spark plugs from a warm engine, put the #1 piston at TDC, thread tester into the spark plug hole, connect the air. The difference between the gauges tells you a percentage of air pressure lost. Say you pressurize the combustion chamber at 100psi. One gauge reads 100 psi, one might say 94. That's a 6% loss.

So, now you have 6% of pressurized air escaping somewhere. If you listen, you can hear a hiss. If you hear it at the intake manifold, you can determine it is the intake valves, if the hiss is coming out the exhaust, it is exhaust valves. If you head it at the valve cover or oil pan, it's rings. If you hear the coolant bubbling, it's a blown head gasket.

That is just a quick, dirty rundown. You can do things, like adding a tbs of oil to the chamber and see if it changes the numbers. If the number is higher, that also indicates a ring issue. If not, most likely a valve or head issue.

It's important to get the valves shut to do the test, so TDC needs to be found for each piston. Usually, a long screwdriver stuck down the spark plug hole and turning the crank with a wrench is how I do it.

[I<3flippyheadlights]

Ah, thanks KFJ. I'll have to try that. I'm glad there us a way to pinpoint my problem.

[tsingson]

I was almost scared to open this thread for fear of the ridiculous (read: asshole) answers he would get but it wasn't even close to what I was expecting. Listen to KFJ, he speaks only the truth.

[Demon I Am]

Yay for this place not being CR!

[tsingson]

Yay for this place not being CR!

You got that right!

[I<3flippyheadlights]

Small update. From last night to today, I drove 55 miles around town. That is a mix of taking it easy and sometimes revving high. (5500 rpms) I lost zero oil. Well zero from what I can tell. I'm so confused....

[Demon I Am]

maybe you should lay off the drinking a little

[I<3flippyheadlights]

How did you know?!

But I'm going on a road trip today, I'll track what I'm doing.

[mhogan0]

Dood do the leak down I'm 100% shure it's ur oil rings but do it anyway just so u can be shure. If u don't have to drive the car every day there's something u can try but if it's ur DD then no go

[kung fu jesus]

I'm not 100% sure it's the rings. If he's staying at or under 5500 and not experiencing oil loss, it could be the valve stem seals or guides.

[I<3flippyheadlights]

Update on this.

After 300 miles of driving and general asshatery (this includes a trip to Orlando and back 200~ miles) I lost/burned a little over 1/4 of a quart. Maybe even 3/8ths. This had a mixture of driving calmly and like a idiot. I guess this is "normal" because its an old car and people would over look it, but it bothers me.

Any ideas? Still planning on doing a leak down instead of shooting at this blind.

[Soledad]

This is just a shot in the dark, but is your PCV system functioning properly? When I first purchased my '90 I noticed abnormal oil consumption and it turned out to be a failed PCV valve.