No expert here, but, the phosphate claim is interesting because it parallels one of Amsoil's claims for why they don't seek API certification on many of their products. Short version is that A* believes phosphate provides anti-wear improvements, but API set low limits to avoid fouling cats. A* counters that due to lower volatility, their oil can have more phosphate in the oil, and less of it gets to the cat.
The SL rating probably requires lower phosphates and that made somebody who knows a little about oils nervous, leading to the warning. But I also believe it unlikely that the newer rating oil hasn't been designed to compensate. Think about it - if the new oil wore the engine out faster, that would be bad for emissions, and it's unlikely that the newer designation would start off with a less stringent lubrication requirement. Such mistakes do occur, but are still the exception, not the rule.
According to information at the
API website for the automotive designations, the later designations always exceed the performance requirements of the earlier designations.
I think we're all trying to learn more here by considering these bits and pieces of information, but when it's all said and done, which is a better method for choosing your oil: Reading the owner's manual for your
diesel engine, and being sure to match what is required, or reading a warning posted on the wall at the local
gasoline race engine shop, and then using that information as a basis for deciding that Cummins has it all wrong? Even if they deal with diesel race engines too, I'm still going to go with the Manufacturer's recommendation on this one!
Delvac 1300, Rotella, Delo all meet the requirements stated in our owner's manuals. Lee Weber recently posted on Delo's near synthetic properties, and if I wasn't using synthetic, there is no doubt Delo would be my first choice.
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