The only way you could check the valve guide is to remove the rocker and spring.

A quart in 100 miles? You must have left a blue cloud behind you that could be seen from a space!

Sounds more like a hole in a piston to me, you have to have HUGE blowby to use that much oil!

Are you trying to keep the oil at the top line on the dipstick?

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!