Originally Posted By: nap
My question is whether, in a car where the manual specifies just “API SN” (without any LL etc), the OCI recommended in said manual would still be valid for an API SN oil that also carries the C3?
Yes I would think so.
Euro C3 is a mid-SAPS oil, the ACEA sequences requires TBN > 6 and SA < 0.8 % with most sitting at or just below this 0.8 % mark. Once they fall below 0.5 % Sulphated Ash they become a low-SAPS C4 oil.
The A3/B4 oils are the high-SAPS oils with TBN > 10 and SA > 1.0 % and < 1.6 %.
Let's look at two typical M1 oils.
First regular M1 5W30 (SN, GF-5, Dexos1-Gen1) has a SA = 0.8%
Second Euro rated M1 0W40 FS (A3/B4) has SA = 1.34 % and TBN = 12.6
So to me, typical US oils rated SN / GF-5 / Dexos1 have roughly the same TBN & SAPS levels as a mid-SAPS Euro C3 oil. The C3 oil has a higher HTHS (> 3.5 cP) so it doesn't pass GF-5 fuel economy tests, but they should be similar with respect to TBN & ZDDP & SAPS levels. I consider typical US GF-5 oils to be mid-SAPS oils myself, they just don't call themselves mid-SAPS oils.
I think a Euro rated oil that is ACEA C3 and API SN and possible Dexos2, to be a good "do anything" PCMO oil. I run full SAPS A3/B4 oils myself, but I have 1 L of Nulon 5W30 Euro C3 oil at home, it's PAO based and is also rated API SN, VW 504/507, MB 229.51 and BMW LL-04. This way I can top up everything from a German light-duty diesel to a Japanese petrol engine without concern.