replacing hydraulic oil in Ferris Zero Turn

hoofty · Sep 22, 2025

The hydro pumps on my Ferris Zero Turn leak and the recommended oil is $16 a quart. They specify Pennzoil 5W-40 Platinum Euro Full Synthetic or Mobil 1 5-40 European Car Formula. The difference is it Meets ACEA A3/B3 A/3B4. Is there something else that is okay to use. I have used sealer and that helps but I still need to add a 1/4 pint every 3 hours. The man that did a partial rebuild has moved the local dealer is too expensive for service. I am considering using the hydro oil from my tractors.

RayIN · Saturday at 9:28 PM

After experimenting, I settled on SAE 30 motor oil in my Hustler ZTR hyd, motors. This is the 4th year on this oil. This winter I'll suction it out and put in new SAE30.
I found the recommended 5W30 thins too much when hot, causing the motors to slip.

oldnslo · Saturday at 9:51 PM

The hydro oil for your tractor is probably around SAE 15 - 20 weight oil so even thinner than recommended and would probably leak even more.

Where are the pumps leaking?

rScotty · Saturday at 10:38 PM

hoofty said:
The hydro pumps on my Ferris Zero Turn leak and the recommended oil is $16 a quart. They specify Pennzoil 5W-40 Platinum Euro Full Synthetic or Mobil 1 5-40 European Car Formula. The difference is it Meets ACEA A3/B3 A/3B4. Is there something else that is okay to use. I have used sealer and that helps but I still need to add a 1/4 pint every 3 hours. The man that did a partial rebuild has moved the local dealer is too expensive for service. I am considering using the hydro oil from my tractors.

It sounds like you are wondering why they specify those particular Full Synthetic Oils? I wonder the same thing.....
The only thing I can think of is that some of the premium full-synthetic fluids will withstand higher temperatures than old dino motor oils without breaking down. But of course the same goes for hydraulic fluids - which are made to run hotter than engine oils, but without the combustion additives. Higher than normal temperatures are directly related to hydraulic oil life.

But whether that is their reason is pure speculation,

Another idea is to contact Ferris and hope to reach someone in the know.

After designing mechanical & hydraulic instruments for 25 years, I rarely ever got a chance to talk to a real customer who actually used the equipment. When it happened It was always a pleasure.
rScotty

hoofty · 2025-09-28T21:55:39-0400

oldnslo said:
The hydro oil for your tractor is probably around SAE 15 - 20 weight oil so even thinner than recommended and would probably leak even more.

Where are the pumps leaking?

Oil is leaking from the top and bottom of the pumps. Motors do not seem to be leaking. I thought that my hydro oil for my tractors was heavier than15-20 but you could be correct. It seems stiffer than the specified 5- 40 at room temp..

big bubba · 2025-09-29T06:40:00-0400

on mine, 5/50 Mobil 1 full synthetic. are both pumps leaking? how many hrs? Parker pumps, hydro gear motors? good luck

D&D · 2025-09-29T07:26:26-0400

rScotty said:
Another idea is to contact Ferris and hope to reach someone in the know.

rScotty

Why bother, odds are they are hydro-gear pumps. Not terribly difficult to disassemble and replace seals.

hoofty said:
The hydro pumps on my Ferris Zero Turn leak and the recommended oil is $16 a quart. They specify Pennzoil 5W-40 Platinum Euro Full Synthetic or Mobil 1 5-40 European Car Formula. The difference is it Meets ACEA A3/B3 A/3B4. Is there something else that is okay to use. I have used sealer and that helps but I still need to add a 1/4 pint every 3 hours. The man that did a partial rebuild has moved the local dealer is too expensive for service. I am considering using the hydro oil from my tractors.