Originally Posted By: jongies3
Don't go off the specs if you want to keep your warranty. Dexos is important to GM and it will void your powertrain warranty if they catch ya using the wrong grade in it.
My Chevy manual does not say dexos is required, only recommended. And there are several TSB's out that state that if dexos1 is not available, then a synthetic of same viscosity is ok to use and will not void warranty. I rarely have followed any OEM's guidelines to the very letter on any engine I have owned. In the ball park, but not exactly. And I have never had a warranty concern.
And 0w20 and 5w20 are the same viscosity. There is no appreciable way that a dealer or GM themselves could tell the difference if they analyzed it. And I have not heard of one dealer analyzing anyone's oil. Even for warranty purposes. I have had warranty work done on many engines, both personal and commercial business vehicles, in almost 50 years and no dealer or OEM shop has even asked me about the oil, let alone tested it. And I have never had to produce a single documented piece of evidence of oil changes, and I have not personally heard of anyone having to. This all is a scare tactic to keep folks in line. I am sure it could happen in the most extreme of situations if the oil was like goo and the engine seized up.
The OP is from Missouri. A 5w20 would work just fine for that application, year round. Actually, the argument could be made very effectively that 5w20 could be a better idea, given the AFM design of those engines and the significantly lower NOACK of a 5w20 compared to 0w20 within the same brand and type of oil.
Some folks just worry too much.