Which is the proper way to add oil to your engine:

1. Add to the full line while the engine is cold (meaning all oil is in the pan).

2. Add to full mark after car has been running.

My question stems from this thought: If you add oil to the full mark after the engine has been running, the oil will be ABOVE the full line when the oil completely drains overnight.

I have always just filled to the full line when the car was cold, as this is the time which should provide the best reference point. Or so I should think.

Sorry if this is a dumb question with an obvious answer. Just been wondering for years.

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E