I have had one bottle of Amsoil Series 2000 75w90 sitting around for a while. If I remember correctly, the maxima 5MT takes 5qts. Would I be able to purchase 4 qts of Amsoil 75w90 MTG (GL4 gear oil), and top up the tranny with the remaining Amsoil Series 2000 75w90? Or is that not recommended?

IIRC, my 4th gen 5MT only took something like 4.2 qts, so it would be very little series 2000 stuff mixed with the MTG. The series 2000 stuff is supposed to be a lot better than the MTG anyways.

 

I dont know what the difference is in those two oils, but redline recommended that I mix MT90 with MTL, so I would assume its ok to mix oils, especially if theyre both the same weight

 

I'd try it... I've mixed in other cars with no issues/problems

I do have straight MT-90 in my 6MT, but if I had 2 kinds of same weight I would mix if I had to.