a factory rep. is going to look at when he comes down to your boat to check out a warranty item. He's going to, right after he shakes your hand and says, "hello, I'm Paul from Volvo", he going to say "let me see the oil you have been using". Hopefully he's going to turn the bottle around and say "OK, CD rating, we can continue". In my case, had it not had the correct diesel rating he would have said sorry about that and turned around and walked. I would have been out the entire repair cost for a 6 month old engine. The additives in oil are different then the ones used for regular automotive engines. I don't know what the difference is but it was sure important to that Volvo guy.