Dave, I'm pretty sure that the
zinc and phos limitations for the API certifications for, say, SM rated
oil do not apply to 15w-40
oil (and they don't apply to 20w-50
oil either). So the short answer is that there is probably nothing on the label to look for, other than something like "Resource Conserving," to really scare you off. That's one of the problems with this ZDDP thing and why I posted that letter at the top of this thread. If it's Brad Penn (even the old Brad Penn) it has the ZDDP that you need. Now you could send a sample off to Blackstone Labs who will check it for $25, but be advised that there are reports that some of their results to tend to be on the "low end" of the scale. That letter that I posted gave me a lot of comfort. It essentially said
"We know our market is aimed at guys that want high ZDDP levels. That's exactly what we're going to give you. And we're not going to get on board with an oil certification that limits our ability to do just that."