1991 Chevy Silverado oil useage

Hi there,

The smoke on start up is a good indication of worn vale stem seals and valve guides. Although you have good compression, the oil control rings may be suspect and a small but constant oil burning may not be visable, a good indication is when you back the throttle percentage off ant high way speed, this will give a very high engine vacuum reading and faulty rings ill show up with a puff of blue smoke then. You can try moving up a weight in the oil viscosity a well.
But oil consumption, if not an external leak, it's going out the exhaust.

Mark (mhpautos)

Try this with a vacuum gauge hooked up to identify ring/s and oil control problem. Or use a compression gauge/leakdown tester

When throttle is opened and closed rapidly and needle falls to 0 and rises to only 24 or less inch

HTH plus the earlier suggestion by Mark