Salesrep,I would agree with Steve about the engine oil being the biggest concern,with respect to quality.
With that,there seems to be some very high quality engine oils on the market today,and rarely problems where oil quality is questioned as the cause of any failure(atleast from my experience).
I have had many seals leaking problems though,on axles,pto's,pinion shafts,etc. and often the seals aren't that old.They have been on seals that were installed from the factory,not seals replaced while in service,so improper seal installation SHOULDN'T be the cause??
Most have been while using synthetic lube,but not all.So my primary concern right now would be having a additive in the lube oil that can keep the seals pliable enough to maintain a seal,especially in the synthetics,which seems to wick through anything that isn't absolutely perfect.This same type of additive in the hydraulic oils would be benificial also,so a thinner oil could be run in cold weather,without seeping out of every joint once it heats up during operation.
FYI,that parasynthetic hy-trans I got from you worked very well in my dumptruck(Ford 8000) hydraulics.My pump is driven by the engine crank via short front mounted driveshaft,and then through a gearbox(to disengaging it).Normally when I fire it up,the pump is noisy(thick fluid)but after I dumped 5gals of that hy-trans(in 20 gal tank,already 1/2 full of petro based hy-trans) is quited right down,even when cold starting.Also the plow raises smooth while cold too.:thumbsup