Just checked the fluid in my 208 and it looked like a mixture of 90wt and ATF. I've drained it and refilled with ATF but started thinking about what might best for my situation. Is there any advantage/disadvantage to running ATF instead of a heavier gear oil? I've looked over some of the previous posts and can buy the line about going to ATF for fuel savings. Are there other reasons? It seems like a heavier oil would have a higher sheer rating and would work better under a load.