i have 4960 4200 hrs,4955 5700 hrs.4455 8200 hrs.4450 9800 hrs. and never have had any ps problems not one! i change trans oil every 2yrs and filters every350 hrs all tey have ever had was hy-guard oil in them keep the coolers blown out and oil level at top of safe line  asked dealer what he thought about using a synthetic because of newer implements using more demand on hyd system and i am worried about heat breakdown of oil and he said why mess with whats working!! so im staying with hy-guard till i have a failure have had same results with rotella  motor oil no failures" NOCK ON WOOD" with oil changes every 150 hrs. use oil samples on every thing and it all checks out fine! but i have seen what a full synthetic motor oil can do in a race motor and they are much better but my dealer keeps  saying why mess with it  I think he has a point so I keep telling him when one of them needs an overhual its getting a full synthetic  oil after break in!

smoke

ps. one time we tested a cup motor with out oil.... drained after 750 laps at darlington  it put out 735hp for 4min 20sec. till it started to bind up  rod bearrings so i do believe in synthetics