First, make sure you have the correct color dipstick for your engine...
Second, make sure with the correct color dipstick that you do not fill the oil to beyond the midpoint between the safe and max lines... lots of discussion on this in archives.
Third, do both a compression and a leakdown test.
Fourth, put new valve stem seals ( and valve rotators and new springs if you can afford them at that time ..cheap done when you have the engine opened up that far anyway... )

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owner of:
1980 manual 240d, manual windows, manual AC, no sunroof, that used to use a lot of oil.