I've been using Allison approved Mobil Delvac 1 synthetic atf in my B500 Allison 6 speed for the last 9 yrs. I send samples to https://jglubricantservices.com/ for analysis because Tom Johnson (Mr.Transynd) is an owner and is available to discuss results on the phone if need be. He was a fluids engineer for Allison/GM and was a key player in the development of the Allison TES295 spec.