AMSOIL 20W-50 100% SYNTHETIC HYDROSTATIC TRANSMISSION FLUID

AMSOIL 20W-50 100% Synthetic Hydrostatic Transmission Fluid is purpose-built to keep zero-turn mowers, stand-on mowers, and riding mowers operating at full speed and responsiveness, even under continuous commercial use. It replaces the 15W-50 or 20W-50 motor oils many OEMs recommend with a formula specifically engineered for the demands of hydrostatic transmissions.

Hydrostatic transmissions operate differently than engines. Oil pressure directly drives the wheel motors, and the tolerances inside those motors are tight. When fluid breaks down from heat or shears under mechanical stress, those tolerances widen, oil pressure drops, and your mower starts losing speed, tracking unevenly, or struggling on inclines. Conventional motor oils were never designed to handle the combination of extreme shear forces and sustained high temperatures that hydrostatic transmissions generate. Transmission temperatures regularly exceed 230°F (110°C) in normal mowing conditions, and that punishment only gets worse during a long day of commercial use in summer heat.

MAXIMIZES MOWER SPEED AND RESPONSIVENESS
In zero-turn mowers from brands like Exmark, SCAG, Toro, Ferris, and Hustler, the wheel motors rely on consistent oil pressure to deliver full ground speed and precise steering response. As wear opens up internal clearances, pressure bleeds off and performance suffers. AMSOIL Synthetic Hydrostatic Transmission Fluid is formulated with high levels of zinc-based anti-wear additives that protect those critical tolerances. Its synthetic base oils naturally resist thinning at elevated temperatures, maintaining the viscosity the system needs to keep pressure up. The result is consistent mower speed and steering response across long days of mowing, not the gradual fade that comes from conventional fluids breaking down.

COMMERCIAL-GRADE WEAR PROTECTION
The meshing gear teeth inside a hydrostatic transmission can literally tear apart the molecular structure of the fluid. This mechanical shearing causes viscosity loss, and thinner fluid means weaker protection against metal-to-metal contact. AMSOIL Synthetic Hydrostatic Transmission Fluid resists both mechanical shear and thermal thinning, forming a durable sacrificial anti-wear film on gear teeth and internal components. In Four-Ball Wear Testing (ASTM D4172B), it produced a wear scar of just 0.42 mm, reflecting strong anti-wear film strength under load. That protection translates directly to longer transmission life and lower maintenance costs for commercial operators running equipment hard every day.

RESISTS HEAT AND MAINTAINS CLEANLINESS
When conventional fluids are subjected to the sustained heat of hydrostatic operation, they oxidize and leave behind deposits that compromise system efficiency. AMSOIL Synthetic Hydrostatic Transmission Fluid uses naturally heat-resistant synthetic base oils with a flash point of 242°C (468°F) and a fire point of 258°C (496°F). These base oils resist thermal breakdown, keeping internal components clean and free of varnish and sludge. Clean internals mean consistent hydraulic response and efficient power transfer season after season, whether you are running a John Deere Z-Trak, a Gravely Pro-Turn, or a Bad Boy zero-turn.

LASTS UP TO 2X OEM DRAIN INTERVALS
AMSOIL 20W-50 Synthetic Hydrostatic Transmission Fluid delivers excellent protection for up to 2X original equipment manufacturer recommendations. For commercial crews, that means fewer fluid changes, less downtime between jobs, and lower operating costs over the life of the machine. Many sealed hydrostatic units like the Tuff Torq and Hydro-Gear integrated transaxles found in residential and commercial mowers are not designed for easy fluid changes, so running a fluid that lasts longer and protects better from the start makes a meaningful difference in equipment longevity.

SPECIFICATIONS AND COMPATIBILITY
Use in hydrostatic transmissions that require 15W-50 or 20W-50 oil recommended for API SM, SL, SJ, SH, or SG. Compatible with equipment from 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. Compatible with other synthetic and conventional motor oils and transmission fluids, though mixing will reduce performance benefits and shorten service life. Aftermarket oil additives are not recommended. AMSOIL 20W-50 Synthetic Hydrostatic Transmission Fluid is Warranty Secure, keeping your factory warranty intact.