car uses approx 1 qt per 500 miles of hwy driving. No signs of oil leakage, spark plugs have a nice grey color, on blow-by into air filter occurs. Exhaust pipe does have some black soot, but nothing very obvious while driving. My first impression from reading all past articles would be valve guides & seals. I would expect blow by back into the air filter in this case.

Leaky valve stem seals should not put blow by into the air cleaner on these cars. How many miles? If over 175k it is probably valve stem seals.

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Jim

You need a top end rebuild, it's not too bad I think I was in the $700 range for mine.