What oil offers best protection for Hydrostat pumps/motors?

[coder]

Guilty as charged... I do have a tendency to do that.
After reading all the posts, that is exactly the conclusion I came to.
M-1 15W50 Fully synthetic. Thanks.

I will take a few temp readings of the Transaxle housing after I have done mowing
with the factory fill. and do a similar set temp readings with the M-1.

 

[coder]

Comment on the Redline ester based oil: Ester based lubricants have one disadvantage. As I recall it is called hydrolitic breakdown.
If I understand it correctly, this may be a sub-optimal for the Hydrogear because of the long OCI, and because the hydros are
open to air via the vent holes. I expect the oil will absorb moisture from the air over time, esp when it is sitting idle.
BTW I have Redline 15W50 in My kawi fr engine and I am on the fence. Runs a bit noisy.
Anyways, in the Hydros, I would probably just use the M-1 red label 15W50. The Mobil support people certainly recommend this oil
for the hydrogear-s.

 

[bruce381]

"Their branded fluid is $20~25/qt and it takes 4.71 quarts. I've not been able to find out anything about this fluids properties other than it contains mineral oil and zinc alkyldithoiophosphate. But for a 1,000 service interval, I guess that's better than most."

LOL for $25 per quart i would get it tested just for fun at least the vis. Then run a quality AW hydrualic oil or motor oil whichever is closest and forget about it.