Out of curiousity how many of those miles have been with the Mobil 1? I bought the truck at 205k so I don't have a good history of the brand used. However I know it was at least serviced regularly because I have the receipts since 70k miles when the PO started ownership. She mostly had it serviced at Jiffy Lube type places, so I imagine the fluid was nothing special, probably just house brand Dextron III.

Have you changed the AT fluid again since you went to Mobil 1? Nope.

Any chance you had an oil analysis done after you first went with Mobil 1 in your AT? Nope.