If you overfill, the "excess" will burn off in no time from frothing or something like that. There isn't enough difference between 7.9 qt and 8 qt to bother, but a half quart will overfill. This used to cause a number of oil consumption complaints from people who insist on having the oil up to the top mark all the time -- always wait until you hit the lower mark (or the oil level light starts to blink once in a while) before adding a full quart.

On the 603, the oil fill was changed from 8.5 qt to 8.0 quart to eliminate this problem. Oil shouldn't go all the way up to the top mark.

Just be glad you don't have the M117 -- 9.5 qt with oil cooler drain....!

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!