My 98 MC, stock 3100, seems to use a lot of oil. I use Castrol GTX High Mileage 10W30, and on average, I have to add 1.5-2 quarts in between each oil change. Does anyone elses use this much oil?

Note: the car does not leak nor does it burn off out the tailpipe.

 

That seems a little excessive to me. I think you should consider a compression check. If the oil gets burned completely enough by the catalytic converter, you may not see it coming out the tail pipe. Good luck!