Mike, now you've really got me wondering. /forums/images/graemlins/crazy.gif I thought it was in my TC-40D manual, but I'll have to check. My tractor is an '01, and I think the fluid was pretty new at that time, so maybe if your tractor is older, that's why it's not in there. My manual is out in the barn, and the snow is still coming down, so I'll look later when I get to plowing. Everyone always suggests it as an alternative for us folks living in the north country to improve cold weather performance and reduce hydro whine. Anyone else, feel free to chime in!