Guys: It's been quite a while since I've been on this forum, but I'm back, and I'd like to start off with a question and request for advice. I purchased a 2015 Silverado 2500 HD DA a little while back, and my free oil changes are about to expire. I believe that the dealer was using Delvac when changing the oil. In my previous Duramax Diesels I used Delo 400 which I could purchase at Costco at a fair price. Does any of you have an opinion as to which is a better oil for the Duramax - Delo 400 or Delvac?
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