hey guys,

Im trying to help a friend diag her 96 Chevy Blazer. I am not terribly versed in the world blazers (i own an import from the japs), but i know my way around cars in general.

The car has the V6 vortec motor in it (not 100% sure on the displacement.... 4.3?) with somewhere around 150K on it. It has developed a large oil consumption prioblem. I have already done quite a bit of work trying to figure this out, but i need some help from some blazer experts such as yourselves.

In about a 120 mile drive somewhere around 2 quarts of oil went misssing. Seeing as that is a profuse amount of oil for an engine to be leaking i figured i would see it in the engine bay somewhere, or the exhaust would be REALLY blue. I looked everywhere and can't find a leak. The car does not leave even a drop of oil on the ground when its parked. The exhaust does not look blue at idle.

Here is what i have already done to try to remedy the problem:
1. Oil change and made sure everything was tight
2. Replaced PCV valve
3. Replaced valve cover gaskets
4. replaced any oil line mentionable

This about narrows it down to internal engine leaks. I know the rings or valve seals could be leaking. The oil pressure seems fairly normal to me, but im not sure what these cars are suppose to be at. Its around 40 on a cold start, 25 once its warm, and peaks around 60 when you really get on it. On the highway it sits just below 40. My question is: Is there a way that the engine could be burning oil at higher RPM's on the highway, but not at idle?

Any ideas or suggestions are greatly appreciated.