Normally I change my oil, Mobil 1 Syn 10-30, every 5k; lost track the last time and changed it after 8k+ (combined city/highway driving.) Wandering what would be a save amount of miles to change synthetic?

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

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

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Robert Fini

'12 ML350 BlueTec, 100k
'06 E320CDI (x2)
'05 T1N Sprinter 2500/Pleasure-Way Plateau TS, 70k
'97 C36AMG, 319k (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)

Should be just fine if fluid level was OK. 8,000 mi. on synthetic oil for me would be my upper limit.

4,000 mi. on regular oil works well for me.

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Question Authority before it Questions you.

I wasn't worried that much mainly because I had to refill two quarts of oil between changes; keeping the oil fresh.

But I noticed the oil being very dark when I changed it.

It's not a Mercedes, I'm driving a Volvo 780 turbo at the moment, the turbo is oil cooled.

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1979 Black on Black, 300CD (sold), 1990 Black 300SE, Silver 1989 Volvo 780, 1988 300CE (vanished by the hands of a girlfriend), 1992 300CE (Rescue).

Jorn, check the Owner's Manual for recommended oil change intervals. Every 7,500 miles is a good rule-of-thumb ... even for older MB engines that used mineral oil. With newer engines using synthetic oil you will see recommended change intervals at 10,000 to 12,000 miles because they run cleaner and the oil doesn't get contaminated as quickly.

Jiffy Lube and oil change franchises will recommend 3,000 mile oil changes because that increases their business, but that's overkill in my opinion. If you check/maintain the oil level regularly and follow the Owner's Manual oil change intervals you should be fine.

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Fred Hoelzle

www.blackstonelabs.com

At your next oil change, take a sample from "mid stream" and send it in. They'll tell you exactly what shape the overall oil is in and can make milage replacement recommendations based on actual (gasp) science. They can also tell you what else is in your oil that shouldn't be.

It's about $20, and they send you the collection kit & pre-paid mailing kit for free.

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A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608

Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL.