This is for my 2008 Scion xB. I'm currently using Redline mt-90 (20k miles on the fluid) and the gears are just not going in as smooth any more. It use to be it be ok once it warmed up but now even at full operating temperature, the tranny still doesn't go in to gear as easily as it did. I read some where that the stock factory fluid and mt-90 don't mix well, maybe that's why it's acting the way it is (It's only had one tranny fluid change). Anyone think dumping the existing mt-90 and using fresh mt-90 would help solve this problem? The other idea I had was trying the Mobil 1 75w-90 gear oil to see if the problem goes away. Anyone hear tried it? It's fairly cheap and available at the local auto parts store which is a plus, but I couldn't find any threads about this stuff when I searched. The owners manual says I can use both GL-4 or GL-5 fluid.