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0w40 redline voa, as said this is for sure the least desirable redline for many reasons already stated, but another reason to not like this starting tbn in the 7's? Anyone have any idea how it can be that low despite the level of CA and other TBN additives? Hemiman - travis anyone? Can't figure this one.
Dunno, sorry. This gets into the additive chemistry that influences total base number TBN, which is an indirect measure of total additives.
I was diesel engine-focused at Mobil, spark engines were for the wimpy Consumer Division!
I can report a typical diesel engine oil TBN prior to EPA lowering sulfur content of diesel fuel was 12, and additives were formulated to slowly degrade TBN level. In a diesel, TBN is primarily a measure of oil ability to neutralize sulfuric acid formed as byproduct of combustion blowby into the oil. Obviously, sulfuric acid attacks nonferrous metals quickly, primarily the journal bearings. And I stated previously that Marine engine oils TBN is 70 because they burn high sulfur Bunker-C residual fuel. It's crude oil slop. The TBN additive in this oil is not robust as automotive diesel oil because marine engines burn the oil too! They never change oil - they just refill the sump! 100,000 bhp ship engines
The other big additive for diesels is polar molecule dispersant detergent additive that holds soot blowby in oil solution. When that additive becomes saturated, soot plates out on engine parts and wears them quickly. Soot is highly abrasive.
I have forgotten, or we didn't discuss, what these additive chemicals actually are. But I'm not gonna google without a laptop - my thumbs are tired!