I wouldn't worry about the 'reformulation'. It has been and still will be one of the best in class.
Additives sometimes are phased out or superseded by the supplier(Lubrizol, Infineum...). If the supplier came out with something newer & better, then it gets used. Same could be said for a base stock, VII, VM, or..... Not everything is in continuum. Kudos to Amsoil improving as technology is made available. Double kudos for not charging me more!!!
It does look like its a tad thicker. Anyone want to wager on what the VOA of the new stuff looks like? more boron? moly? phos? a couple drops more of ester base oil?
2 different data sheets that I have for 75w90:
75w90 Amsoil
visc at 100 16.7 / 16.9
visc at 40 109.1 / 114.7
ViscIndx 165 / 161
brookfield 68150 / 69420
flashpt 220 / 210
pourpt -48 / -50
falex 2500 / >3500(rumor >4500)
4ballEP 66.17 / 75.64
Who would've thought that going thicker with gear oil is better for gear life
BTW, the 75w110 and 75w140 looked improved in a similar way too.
If you read Amsoil's old gear oil study, you see where certain 'other' brands beat them in Falex and 4ball tests. The new numbers put Amsoil into the #1 spot