I have a good friend with an 88 190E 2.3L with 210K. He is using 1 quart of oil every 500 miles. Is this indicative of bad valves or bad piston rings? No oil in the overflow tank.

He is going to get rid of the car and I am thinking of doing the work and reselling. The rest of the car is in great shape.

How much would a machine shop charge to do the valves?
How much for a shop to do the the rings?
What would be a good purchase price for me?
What could I ask when it is put back together?

thanks for the thoughts

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1996 (W210) E300D 86K - Traded in for a Lexus
1992 (W124) 300D 2.5 Turbo 202K - Sold
1983 (W123) 300D, 146K - Sold
1970 280S, 263K - Sold - Beginning of addiction