Originally Posted By: CATERHAM
How is a 12cSt KV100, 3.5cP HTHSV 0W-30 which is as close to a 40 grade oil as makes little difference "way too thin for a light duty 2L diesel"?
In Europe where small diesels are very common even lighter C2 0W-30s are specified.
You'll never go wrong running the lightest oil the manufacturer specifies. Using something heavier may make you "feel better" but the decision is not rationally based and would be totally counterproductive.
Contrarily, 3.5 is the "natural" HTHS for a Newtonian 30, which is clearly what the grade is based on....the inclusion of HTHS "minimums" came in because Non Newtonian oils displayed shear thinning that lead in cases to failure...that does NOT make 2.9 the "natural" 30 HTHS, merely the "minimum"...prior to the 2013 changes to J300, you could also have made the same claim re 5W40.
But I do agree, if it carries an actual BMW specification, and that spec is approriate for the engine, then the oil is fine...I'd choose less of a Unicorn, if I had no absolute need for the 0W part...and there are plenty of them.