20W-50 Synthetic Hydrostatic Transmission Fluid

High-zinc formulation fights wear and helps preserve mower speed and responsiveness.  – See Reviews Below!

Here in Sioux Falls the top landscaping companies are using this. They see almost instantly the “extra power” that didn’t exist before. The fluid is what transfers power so a motor oil version’s additives interfere with proper power transfer and heat absorption. It’s one of the “secrete” products we want to get the word out about!

20W-50 Synthetic Hydrostatic Transmission FluidIt fights wear and viscosity loss during continuous, severe-service operation, maximizing mower speed and operability. Unlike motor oils, Synthetic Hydrostatic Transmission Fluid is purpose-built to withstand the unique demands of hydrostatic transmissions. It lasts up to 2X original equipment manufacturer (OEM) recommendations, helping professionals save money and reduce downtime.

Maximizes Hydrostatic Mower Speed & Responsiveness

In many zero-turn mowers, oil pressure drives the wheel motors. Fluid that fails to protect against wear can cause the tight tolerances in the wheel motors to widen, which reduces oil pressure and erodes speed and responsiveness. Fluid that thins at high temperatures can have the same effect. AMSOIL Synthetic Hydrostatic Transmission Fluid contains high levels of zinc-based anti-wear additives to help maintain those tight tolerances, while its synthetic base oils naturally resist viscosity loss in extreme heat. As a result, it helps maintain mower speed and responsiveness for increased productivity.

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Product Data Bulletin for the Hydrostatic Fluid you can download and print

Commercial-Grade Wear Protection

Transmission fluid must form a thick, durable film on gear teeth and other components to guard against metal-to-metal contact and wear. The mechanical action of meshing gear teeth, however, can tear apart – or shear – the molecular structure of the fluid, leading to viscosity loss. High heat can also cause the fluid to thin. The thinner fluid can fail to protect against wear, reducing mower life and increasing maintenance costs. AMSOIL Synthetic Hydrostatic Transmission Fluid’s naturally tough synthetic base oils resist viscosity loss due to shear and high heat, promoting the formation of a durable sacrificial anti-wear film on components that helps extend mower life.

Keeps Hydrostatic Systems Clean

High ambient temperatures, combined with hydrostatic transmission temperatures that can exceed 230ºF, cause some conventional fluids to break down and form harmful deposits. AMSOIL Synthetic Hydrostatic Transmission Fluid features naturally heat-resistant synthetic base oils, which reduce deposits and help keep equipment clean and running properly season after season.

  • Fights wear for smooth, responsive operation
  • Purpose-built to outperform motor oils
  • Resists high heat and shear


Use in hydrostatic transmissions that require 15W-50 or 20W-50 oil recommended for API SM, SL, SJ, SH or SG, including (not limited to) those found in zero-turn, riding and stand-on mowers made by SCAG*, Toro*, Ferris*, Snapper Pro*, Gravely*, Ariens*, Exmark*, Walker*, Hustler*, Wright*, Dixie Chopper*, John Deere*, Husqvarna*, EverRide*, Bad Boy* and Cub Cadet*. Not for use in engines.


AMSOIL 20W-50 Synthetic Hydrostatic Transmission Fluid is compatible with other synthetic and conventional motor oils and transmission fluids. Mixing AMSOIL oils with other oils, however, will shorten the oil’s life expectancy and reduce its performance benefits.

Aftermarket oil additives are not recommended for use with AMSOIL transmission fluids.


AMSOIL 20W-50 Synthetic Hydrostatic Transmission Fluid is recommended for 2x original equipment manufacturer (OEM) recommendations.


AMSOIL products are backed by a Limited Liability Warranty. For complete information visit AMSOIL Warranty Information.


This product is not expected to cause health concerns when used for the intended application and according to the recommendations in the Safety Data Sheet (SDS) . An MSDS is available via the Internet at www.amsoil.com or upon request at (715) 392-7101. Keep Out of Reach of Children. Don’t pollute. Return used oil to collection centers.

*All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use. All products advertised here are developed by AMSOIL for use in the applications shown.

Buy in the Sioux Falls AMSOIL store near . or use this Online link to the Amsoil sale page if you are outside of the area.

Reviews of the Hydrostatic Fluid 20W-50

Best Hydro pump Fluid

By  BRUCE,  a  Verified Buyer  from  Port Charlotte   on  December 27, 2022

Work’s amazing pumps more responsive quieter run cooler also good price compared to competitors

Fixed my mower

By  JOHN,  a  Verified Buyer  from  NC  on  April 26, 2022

Had trouble with steering my zero turn mower for years. The dealership couldn’t fix it. Had 130hours of use. Servicing the transmissions was called for at 400 hours. I decided to service the transmissions anyway and use Amsoil’s product and new filters. Problem solved. I rarely leave reviews so this means I am honestly impressed.

ZTR 20W-50 Hydro Trans Fluid Better Than Ever

By  BRYAN,  a  Verified Buyer  from  Southern Indiana  on  June 21, 2022

Good stuff – I was always surprised that my two ZTRs (Great Dane & Country Clipper) specd 20W-50 motor oil for the hydraulics, but it worked for 10+ years. I was starting to have a whine and a small leak in the CC ZTR. I saw this and liked that it was 20W-50 and specifically for ZTR hydros. Switched both to this and they run cooler, seem more responsive, and the whine and small leak have went away.


Simply the best: Tested! Tried! & True! Oh MAN!

By  RANDALL,  a  Verified Buyer  from  Rusagonis, NB  on  August 23, 2021

One particular customer I have figured changing the engine oil to Amsoil would be enough. I challenged his to change the zero turn and he remains totally impressed. His statement to me was: How can these products make such a difference? I just simply stated: they are Tested! Tried! and True!