hello, my car is a 96 Bonneville with the NON supercharged engine, and 220k. The problem started with white smoke after sitting in traffic, it is not coolant, it smells like oil, the exhaust pipe is black, it doesnt use any coolant , but does use a lot of oil if car is being drivin slowly or in stop and go traffic. I recently drove 300 miles round trip on the highway and the car used absolutely not one drop of oil. I replaced the pcv with a kit that included pcv, two O-rings, spring and cap. this didnt help. I checked the uim , it has a date of 2008, I am assuming the lim gaskets were replaced at the same time but not certain. finally I checked the spark plugs, the front plugs look normal with a tan color, the 3 plugs facing the firewall have black crusty residue on them. the engine is smooth and peppy, with no signs of engine trouble, any help is appreciated .

do a compression test, if the rear numbers are low, add a spoonful of oil and retest. if its higher the problem is rings and or worn cylinders, if it stays the same the oil is coming from above somewhere

If the front bank of plugs are clean vs the rear bank being sooty, I'm suspecting the rear bank is sucking oil from a bad LIM gasket. And because the upper plenum says 2008, that can't be a guarantee that the LIM gaskets were done.

I suggest doing the LIM gaskets and at least changing the plenum gasket too.

But this doesn't also rule out Justin'* idea of a compression test. So you can do that too if you can.

its a good reason to do the test, if the compression is good your likely looking at what mike said

thank you for the quik responses. I was afraid you were going to tell me it was low compression or lim lol. I was hoping it was possibly a simple fix such as a vacuum issue etc, but at this stage I think its best to probably do what you suggested and check compression and if that'* good change intake gaskets grrrrrrrr. Thing is the car is great otherwise, and I love driving it, motor, trannny etc feels like it has another 100k left in her so I think its worth it to fix, thanks guys!

Yes, its a fun car to drive and it will last a long time as long as you take care of it. Don't skimp out on the real needed things such as LIM gaskets.

You can still have worn oil rings and have good compression. Causes of burning of are valve stem seals or guides, oil control rings on the piston, pcv valve or o-ring and the lower intake manifold gasket. Id go after the intake manifold first considering it was done in 08.

Have seen the rings break on the valve stem seals....think there is a TSB on this....