Yeah, this is an old thread.

Running the engine overfilled can cause the crankshaft to churn up the oil and cause cavitation. I don't think it would really accentuate a headgasket leak, though. However, I would remove the excess oil.

I once pulled almost 9 quarts of oil out of an M104 during an oil change which had the previous oil change performed by the dealer. The "max" level on the dipstick is 7.4 quarts.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record