Originally Posted By: Trav
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If an actual owner has had good results with a given grade, I'd pay some heed to that.
If its not in spec anywhere in the world only an voll idiot would take that leap of faith.
My god 20w is not even spec for Finland which has regions up to the arctic circle.
Just because someone tries it and reports having luck with it doesn't mean everyone else should jump with the same enthusiasm.
Who is going to pay for that very expensive BMW engine when it all goes up the Suwannee, the guy who recommends 5w20?
I think not!
I do appreciate that your understanding of motor oil is limited particularly with the concept of operational viscosity.
I very much pay heed to the oil recommendations of BMW, particularly the minimum oil pressure test spec's for a given engine. In that regard I have no interest in seeing how light an oil I can run by BMW by testing those OP spec's, consiquently there is "no leap of faith" or "luck" involved in the oil that I run.
Oil viscosity is temperature related. If, as I mentioned previously, you keep your sump oil temp's below 90C you will not test the minimum OP spec's for your engine running a 20wt oil. Consiquently if one has oil gauges to become familiar with the oil viscosity characteristics of your engine, then you too can benefit from running a 0W-20 oil in the winter in your BMW or for any make for that matter.
And yes, before the advent of high VI 0W-30 and 0W-40 oils BMW did recommend 5W-20 oils for cold weather running as did other German OEMs such as Porsche and Audi.