I have no idea whether Amsoil tests their oils against ASTM D6922 but they better. That would constitute pretty significant negligence if they did not.Sorry but by that logic, Amsoil and numerous other oils are "unsafe", which we know is not necessarily the case - I'm pretty sure you're not saying that Amsoil is unsafe to use, or are you? Not trying to start a fight, but insistence on a test being passed to be safe, well, passing a test isn't possible when an oil isn't submitted or put through that test.
In any case, let's fall back to the M1 discussion and my question, which you didn't answer: if, in fact, it was unsafe to mix viscosities, then wouldn't ExxonMobil, one of the largest producers of petroleum products in the world, have put out some sort of warning by now?
And you don’t have to be sorry, I was just stating facts. If some blender was producing an oil that failed ASTM D6922 then that would be a very bad thing. All of which is separate from performance specifications which define other things about the oil. That’s what we were talking about. You could still have two, or 10 crummy performing oils that are miscible in your “frankenbrew” example. This is where people miss the boat on miscibility as they mistake that for performance.
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