I agree with Jet on that one. I've been using Amsoil for years and will continue to until I die. The 10w-30 is an awesome oil, but would highly recommend the High Performance 10w-40 by Amsoil. It is 229.3 rated and the way Mobil has been in the last several years, the 10w-40 Amsoil will not change the product line like Mobil has.
If you look closely at the Amsoil 10w-40 specs, you will see that it's also rated for the newest Diesels out there. This CI-4 rating is just out but it also meets the most toughest specs from Mack, etc.
I will say that the Mobil Delvac 1, which is a 5w-40 oil is terrific, but when they came out with the new CI-4 spec, the pour point changed dramatically.
I know that everyone of us had our opinions on oil, but no matter what oil you use, keep it changed regularly. It's such cheap insurance!!