Have you puled plugs to look at them recently? If could be burning it.
Another thought is to look at the PCV valve and then check in the intake to see if you have a lot of oil residue in there. Blowby (pressure leaking past the piston rings) will force oil mist our of the crankcase and into the intake.
How many miles is this happening in?
Have you run a compression check?
How many miles on the car?
The good news is that it could also be the valveguides and these are much easier to replace than to rebuild the shortblock.
Chris