I have not tried the 75/90 in the hydrogear but tried it it a wore out ford car engine and it foamed real bad . My Case loader uses hydraulic pumps and motor and it has stickers on it that warns to use only type F transmission fluid because the type A will compress and make the hydraulics spongy. So if you are looking for a experiment The Type F transmission fluid might stiffen up the response on the hydrogear. I also used the 20w/50 oil with no problems.