We have used Amsoil 75w-90(svg) severe gear synthetic extreme pressure lubricants in the tranny of our Apex 90.We noticed a significant temp. drop in the fluid itself from some of the previous brands we were using.I am not saying this is going to save any trannys,but the lubricating qualitiesand heat dissipation this provides can`t hurt.Contact kcmarland4oil.com and he can be of great assistance with this product.