They also say “In general, oils should be compatible with each other. It is not likely that you would form gel by mixing the two oils”
And then there’s this
"You would be better to run all Mobil 1 synthetic motor and run it longer than mixing it with “regular oil.”
Suppose, you’re adding a quart or two because you’re low on oil. Is this “expert” suggesting that, you just run your engine a quart or two low until you can find some Mobil 1 to top it off with? Context matters in situations like this.
Don’t know that I would put a great deal of faith into what a single dealership’s service dept posts on the internet. These are the same people who send out emails like this. Anyway there’s a lot of “nothing bad will happen but we don’t recommend it” going on.
No really, seeing that all it takes to be an Amsoil distributer is a credit card. Literally anyone can be an Amsoil distributer it’s MLM outfit basically. Also for the longest time Amsoil’s oils didn’t carry any kind API certifications. It was always basically, “Just trust me bro”. I think these days most of their line up does carry API certifications. And yes, I know their oil is supposedly quite good and they’ve been around for quite a while now, and they have their fans.
I’m aware of how oil is formulated and whatnot, I’ve lurked over at Bob’s The Oil Guy for years now. Here’s the thing though. If both oils you’re mixing both meet the standards for your particular car, and you’re changing it on time; you’re almost certainly going to be fine.