Many of gears have spun many of miles on dino, 75w-140 is only really available in synthetic $$$$. With that said my D44s have Mobil1 75w-140, lol because I couldn't make up my mind. I think I was looking at 80w-90 at the time. Mobil1 was $16qt. ouch! Not sure I would do it again because of the...