Originally Posted By: tmcafe
TBut what I was wondering is why the JASO standard sets the sulphated ash max at that value. And usually the best products are as far from the max. allowed values as possible--it's the "exceeds" vs. just "meets". Not sure what higher ash content means for the engine. Again, I assume the max set by JASO is really the threshold value.
From the Rotella website: "Oil ash contributes to combustion chamber and spark plug deposits." But that begs the question, as you allude to, why an oil company would simply "meet" the 1.2% and not exceed it by a wide margin.
I found
this to be the answer why: "A noncombustible motor oil residue resulting from
detergents and metallic additives." In other words, ash is a function of the additive package.
If you browse around this site you'll find again and again references to how oil additive formulas is really a tricky balancing act. It's not simply a matter of loading up on Zinc or Phosphorus as too much of those can be harmful in other areas of oil performance. I'm sure they could make an oil with an ash level approaching 0%, but that would imply a greatly reduced level of detergents and metallic additives. You'd have a low-ash oil that performed like ... well, not well.
The JASO spec for ash is 1.2%, and the new Rotella 15W-40 CJ-4 comes in at 1.0%. I'm pretty sure Shell's primary objective was not to meet and slightly exceed the JASO spec ... their primary market is trucks, and I think the new regulations on Diesel emissions is what drove them. Meeting JASO is just a happy byproduct of their trucker market quest.
Originally Posted By: tmcafe
The other thing is how oils that meet SH stack up against SG. What's the difference between SG and SH. Why is it that some suspect that m/c oils should still be SG rated? Yes, part of it is the percentage of anti-wear.
So what makes SH not meet SG? Why is it that even top of the line m/c oils still clearly state that they meet SG?
Good questions ... and ones I can't answer. It's always baffled me how an oil can SJ, SL and SM (or SH and SG) ... at the same time. Apparently there's a way to meet the newer, presumably more stringent specification and still meet the older. I don't know enough about the specifications to know how that's possible.
I think the emphasis on SG for motorcycles is the perception that the higher levels of Zn and Ph in those oils is critical for motorcycles. I'm not so sure of that, but I'll leave it to others to argue the pros and cons. Certainly not for my bike -- a Goldwing -- whose engine behaves more like an Accord than a Hyabusa.
I'm not sure of this -- but I'd love to know more -- but I
think the newer oils (CJ-4 / SM) require specific refining techniques and better base stocks. That *may* explain the SG to some degree -- it's easier and cheaper to get. I could be wrong on that ... pure speculation on my part.
Originally Posted By: 02zx9r
Trust me if any one knows about Rotella, its Don. He is in love with this oil, as many others are, and for good reason.
I seized on Rotella as a kind of new hobby to explore and understand. I could just as easily have settled on Delvac or Delo for that matter. Or Wal-Mart SuperTech ... an oil that Sunruh (from this site) says good things about.
Lots of people wonder why Shell isn't more aggressive in marketing to the motorcycle market. My view is that right now they're perfectly happy with the "cult" status and the word of mouth advertising (like this post) they get. Fleet and heavy equipment is their primary market, and their marketing message is squarely focused on it. Emphasizing motorcycles would dilute that message. So they stay focused on trucks, and allow crazy people like me to talk up Rotella for motorcycles.
