Originally Posted By: Dennis_E
This is exactly my point - API SG/CF. CF not C?-4. As told to me in another thread CF is most certainly not a C?-4 lubricant. Yet many think Mobil-1 is one of the best. I would like to think so too but I'm just having trouble not getting past the C?-4 specification. Harley put it there for a reason and I don't know enough about lubrication to understand why Mobil thinks CF is OK.
Hi Dennis --
The "C" portion of that designation refers to the diesel specification; the "S" portion of those other things refers to gasoline engine specifications.
One of the things taking place in the diesel oil space is more and more stringent Environmental Protection Agency (EPA) rules about diesel oil, all in an effort to lower the pollutants emitted by diesel trucks.
So as time goes by -- and the "C" specifications are superseded by newer ones -- some elements of the oil are modified. For example, the "sulfated ash" levels of the newer diesel oils are reduced from earlier spec levels.
Note: It's peripheral to your question, but just a trivia -- it was the sulfated ash level of the Rotella CI-4+ oil that prevented it from meeting the JASO-MA specifications. But the newer CJ-4 has reduced its sulfated ash -- as part of EPA mandates -- and thus it now meets JASO-MA. It's not certified JASO-MA because that implies money to bear the label on the jug, but by all indications the oil meets the spec.
Anyway, the point being that as the diesel oils go to newer and newer spec levels, some additive proportions change. The CJ-4 has a lower ZDDP than was allowed under CI-4+, and most like CI-4+ had less than earlier oils.
Now, my understanding is that newer oil specification levels are supposed to meet or exceed earlier spec performance. So a CJ-4 (newer) should exceed CI-4+, which should exceed the performance of earlier spec levels.
Things get really interesting -- and I don't claim to fully understand it -- but read a bottle of Rotella Triple Protection 15W-40 ... it says, "Meets API Service CJ4, CI-4 Plus, CH-4, CG-4, CF-4/SM, SL, SJ." What that's saying is it meets the newer spec and the older specs.
We can't dismiss the possibility that Harley intentionally clouds the issue to increase sale of their labeled oil. All bike manufacturers do something like that -- Yamaha calls for Yamalube 20W-40, which is difficult to find other than their brand, but in truth any good 40-weight will be just fine.
My guess is Mobil 1 20W-50 will be just fine in your Harley. There's simply a bunch of people who use it.
But if that'll make you lose sleep, then buy the Harley oil and rest easy.