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What Engine Oil - manual spec vs. Mobile1 0w40? Sorry for the dumb subjective Q.

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First of all, can anyone remind me what the official spec in the manual is? My guess is NOT synthetic, but would like to know. I don not have an owners manual to look up.

Second of all, I run mobile1 0w40 on my E39 M5 per mobile1 website recommendation. I'm in Chicago, so below32F is quite common. That said, it would be nice to keep the same oil in my garage, but if anyone has any reason I shouldn't, or simply because that's not what the car "desires", please let me know.

Please, I know there is no absolute answer to my 2nd question, and I'm open to your opinions and comments. Especially if someone has a BAD example or data on using 0w40 on E34M5. BTW, it is 1991, with 110k miles.

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· Moderator Emeritus
4,348 Posts
My personal opinion may not be universally welcomed but my gut is telling me
this after having many European S38's top ends open is this.
Do NOT use Castrol edge if your car spends lots of static garage time.
If it's used every week, then cool.
It's a great oil that offers great protection at the thermic & shear extremes
that a hard used engine will generate on track etc.
But it's for an engine that is being turned & used...every week.

I have used Quantum Synta & Castrol Magnatec 10w/40 semi synthetic.
( Not true synthetics from a chemical stand point but highly developed
blended oil)
I am proud to say that I have clocked exactly 100,000 miles this week in my
8 yrs ownership out of 183,000 miles using the above in my 3.8:thumbsup:

If you live in high altitude / more cold climates where ambient temps
are below -15 Deg C, then refer to the owners manual for viscosity recommendations.

I feel that regular oil changes are the key to longevity, not fancy oils that
were not in existance when the S38 engine was developed.
Oil technology has indeed moved on but so has Metallurgy & EGR of modern
production engines.

BMW's own acceptable oil consumption figures for the S38 would tend to support general
perception that whilst some engines may use a litre (35.2 fl oz) every 3000 km or less,
some will use that every 800km...& its acceptable over this range !
That's one mighty big production & wear tolerances to throw very expensive
full synthetic oil at when, over a 6000 miles service interval, you could add
10-12 extra litres to the engines oil change 5.7 litre bulk fill !

Anyhow, I could go on...I won't.:blabla:

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