My 4 work tractors get used on average about 10 hours per year. I think the minimum Hytran-change window is 100 hours (The Sundstrand service manual claims you can go ~400 hours (or something like that) with a filter in the system in some situations). That means at the current rate my tractors will go at least 10 if not more years without a Hytran change. The ones that are not operated during the winter sit in an unheated, partially un-sheltered barn. There's plenty of opportunity for condensation to form inside the rearend. I don't want that rusting anything. And nothing will rust so long as there is Hytran in the rear. This would be even more critical if my tractors had to sit outside. I have had a couple of tractors that I drained WATER out of, yet had no rust whatsoever anywhere inside. I can't be so sure. One time I bought some of the off-brand stuff, and I put some in a dish and some Hytran in another dish. I put some water in both. The Hytran dish formed sticky globs, and the Off-brand dish did nothing. The water and fluid stayed separate. I have also had a couple of other tractors that had less hydro whine after draining out fluid of questionable origin and replacing it with Hytran.
Just because they both meet the same specs doesn't mean they are the same. 5 gallons will take care of 2 tractors with some left over for ~200 hours each if you want to sit in the middle of the change interval... That's like 19 cents per hour of the tractor's operation. That's still pretty cheap in my opinion
