Hi, Jorn.

As they say, "Your mileage may vary..."

Oil longevity is a direct function of the type of driving you do (city/highway, constant cruising or constant start/stop, etc.) and the environment in which you do it (temperate climate, desert heat, arctic cold, etc.), so making an absolute statement about your "safe" oil change interval is difficult.

You don't say the car for which this question is posed, but the factory-recommended oil change interval on my '97 C36AMG is 7,500 miles; stretching that to 8,000 miles shouldn't be very detrimental. Our 1999 E320-4M has the Flexible Service System (FSS) that tells you when to change your oil based on various driving parameters as measured by its sensors.

All that being said, I change the oil (Mobil 1 5W-30) and filter on my C36AMG every 5,000 miles and on the E320-4M as directed by the FSS. Some guys will say you should have an oil analysis done to check the internal health of your engine. I say you should check the owner's manual and change the oil at least as often as recommended.

Best Regards,
Rob

__________________
Robert Fini

'12 ML350 BlueTec, 111k
'06 E320CDI (x2)
'05 T1N Sprinter 2500/Pleasure-Way Plateau TS, 72k
'97 C36AMG, 325k (son's)
'94 E320T, 249k
'93 190E Sportline LE, 168k (daughter's)
'84 190E-2.3/5spd (Stage Rally Racer)
'66 230 W110 Sedan (Barn Find, Vintage Racer build in progress)