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GM Dexos, API-SN, GF-5 and Your Motor Oil
So back in 2011 GM did something a little unprecedented by creating its own specifications and review board for lubricating oil that was separate from API (American Petroleum Institute - a review board on which a GM member already sits.) The certification an oil receives from that new board gets the label 'dexos1' or 'dexos2' (the manufacturer of the oil also has to pay GM for the test, and provide a royalty on every sale.)

This in itself was mostly harmless, except the fine print in some of the manuals (including my vehicle in 2014.) In these vehicle manuals, GM took it upon itself to inform its customers that if they didn't use dexos oil, it 'may result in engine component damage that will not be covered under warranty.'

That statement ran afoul of FTC laws, and the FTC put a bulletin out informing customers of GM vehicles that their warranties can not be voided UNLESS GM can prove that the owner did not utilize dexos oil, *or an equivalent*, and that said oil specifically caused the damage. Pretty tall order to prove that, as a non-dexos oil that meet or exceeds dexos1 qualifications (API-SN, GF-5 both come close and in some oils do exceed dexos specs) is basically the same damn thing. Not only that, but you could always flush your oil and put dexos in before you rolled it into a GM shop.

Furthermore, now that GM moved to dexos1 gen-2 (last year), to the best of my knowledge, there is no longer any 'synthetic blend' type dexos oils being manufactured. Synthetic blend is what was recommended for my car, and it is what I've used since I bought it. Of Advance Auto, Walmart and Autozone locally, none of them are carrying synthetic blend dexos1 oil. (Seems like I can still order them online - but I've never ordered oil online, and am not sure why I would be put in the position of needing to do so?)

General online research tells me that there's little to no difference between dexos and GF-5/API-S.

What do I make of all of this? I think GM found a way to increase revenue and put oil manufacturers in a position where, if they wanted access to something like 24% of the auto market in the United States, they had to pay to have their oil tested, and then pay royalty to GM for the dexos label. They then proceeded to use fear on their car owners by telling them if they use anything other than dexos-marked oil, they could ruin their 100k/10 year powertrain warranty.