In preparation for my upcoming winter oil change, I was at an auto parts store hoping to find 10w30 diesel oil for my 7.3 PSD and of course all that was available was 15w40. I asked the counter man if there was any 10w30 available and he looked at me like I was speaking another language. He then went on to say he had straight 30 weight for winter use. I sad to him no one would run straight 30 weight in the winter. He looked at me like I was nuts. Hopefully, he doesn't have a diesel pick up. LOL