SAE 50 Long-Life Synthetic Transmission Oil 

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Engineered for 500,000-Mile Service Life in Over-The-Road Trucks

SAE 50 Long-Life Synthetic Transmission OilAMSOIL SAE 50 Long-Life Synthetic Transmission Oil is specially formulated to meet the demanding requirements of manual transmissions found in high-torque, heavy-duty line-haul trucks and other commercial applications. Its synthetic base stocks and premium additives help reduce gear and bearing wear (see photos), improve shifting and extend transmission life throughout drain intervals of up to 500,000 miles/five years. Compared to conventional fluids, Long-Life Synthetic Transmission Oil can help operators reduce maintenance costs and increase productivity.

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Year-Round Performanceftf_photo_transmission

AMSOIL Long-Life Synthetic Transmission Oil’s high viscosity index translates into better high- and low-temperature performance compared to conventional fluids. In cold weather, it provides easier shifts and reduced fluid drag for increased fuel economy. Its exceptional thermal stability inhibits chemical breakdown and sludge formation at high operating temperatures to help transmissions run cleaner.

Resists Wear

AMSOIL Long-Life Synthetic Transmission Oil’s synthetic base oils withstand the pressures of high-load, high-torque applications. As a result, it resists viscosity loss due to mechanical shear to provide a durable lubricating fluid film for increased wear resistance and longer transmission life.

To prove its effectiveness, AMSOIL installed SAE 50 Long-Life Synthetic Transmission Oil in line-haul trucks and placed them into real-world service.

After 500,000 miles, a transmission was disassembled and inspected by a calibrated ASTM rater. Results reveal Long-Life Synthetic Transmission Oil provided outstanding wear protection in all critical components. Examples include the input shaft main drive gear and output shaft bearing, which both earned high merit scores of 8 out of a possible 10 for wear. In addition, both components showed no scuffing, spalling or corrosion, scoring perfect 10s in all areas.

Inhibits Foam

Churning gears introduce air into the fluid, causing foam. When bubbles between gear surfaces collapse, metal-to-metal contact and increased wear result. Long-Life Synthetic Transmission Oil contains foam inhibitors to ensure formation of a strong lubricating film and excellent wear protection.

Seal Friendly

Long-Life Synthetic Transmission Oil is compatible with seals to help prevent leaks and extend seal life.


AMSOIL SAE 50 Long-Life Synthetic Transmission Oil is excellent for use in manual transmissions requiring an SAE 50 lubricant found in heavy-duty equipment. It is recommended for applications specifying any of the following:

  • Eaton PS-164 Rev. 7
  • API GL-1 and MT-1
  • Navistar/International TMS 6816
  • Rockwell/Eaton/Fuller CD-50 (PS-081)
  • Mack TO-A Plus
  • ZF Freedomline
  • Meritor 0-81

Many marine applications as well as racing applications call for a 50 weight transmission fluid so this is also used for those applications.

In stock in Omaha

A regular stocked item in the Omaha store. We keep gallons and the 5-gallon pails. Call to check at 402-933-3902

Field Studies & Performance Data

Diesel Fleet Fuel Economy Study (G2904)


Diesel Fleet Fuel Economy Study in Stop-and-Go City Conditions (G3086) (368k PDF)


Service Life

Follow the OEM drain interval for synthetic oil up to 500,000 miles or five years, whichever comes first.

For warranty information, visit AMSOIL Warranty Information

Customer Reviews

Comments about SAE 50 Long-Life Synthetic Transmission Oil

Put it in transmission on my Kenworth, noticed smoother shifting

How would you describe yourself?
I use AMSOIL products for my business
What kind of vehicle/equipment do you have?
Personal cars and class 8 truck

Bottom Line Yes, I would recommend to a friend