Is it ok to run 15-40 oil in my 2001 GMC. It is z71 5.3 4x4 ex cab. I had a mechanic tell that I should run a thinker grade than I currently use. I use 5-30 now. Said he ran SuperTech 15-40 in everything he owns. I've thought about trying it because of my quart or more oil burning during 3000 mile oci. I've actually thought about switching to Delvac 15-40. I currently use Mobil Super 5-30 and used Maxlife 5-30 before that. Bought the truck new and it now has 213,000 miles it.