What is the Best Transmission Fluid?

AMSOIL Signature Series Synthetic ATF excels at fighting heat and protecting gears and clutch plates, as demonstrated in severe testing.

April 16, 2021

We believe AMSOIL Signature Series Synthetic Automatic Transmission Fluid is the best transmission fluid available. We don’t base that claim on wishful thinking – we punish our products in real-world, severe-service applications. Read on to see what our grueling testing protocol revealed.

The ATF job description

Your transmission might be the most complicated component of your car or truck. Today’s transmissions are smaller and must endure higher horsepower and torque, all while delivering smoother shifts with longer fluid-life recommendations.

These modern designs also pack in an enormous number of gears, clutch packs and narrow oil passageways that require a steady supply of high-quality fluid to function. Transmissions used for hauling or towing are subjected to enormous torque and increased heat, the number-one enemy of any transmission. For optimal vehicle performance, the best transmission fluid must….

  • Fight heat
  • Function as a hydraulic fluid
  • Deliver the right frictional requirements
  • Protect gears from wear

Check out this post to learn more about the work of transmission fluid.

Reserve protection after 180,000-mile severe-service test

It’s easy to say AMSOIL will outperform other fluids at the above tasks, but what’s the evidence?

To demonstrate its capabilities in severe service, Signature Series Synthetic ATF was installed in a fleet of Las Vegas taxi cabs and subjected to a 180,000-mile (289,700-km) severe-service test. The vehicles routinely endured demanding stop-and-go driving while loaded with passengers and cargo in extremely hot desert temperatures, placing tremendous stress on the fluid. Following 180,000 miles (289,700 km), a transmission was selected for analysis.

After 180,000 miles (289,700 km) of severe service, an independent, third-party lab revealed that Signature Series Synthetic ATF resisted oxidation longer than required for new fluid to meet the Chrysler ATF+4 specification.

The Aluminum Beaker Oxidation Test (ABOT), an industry-standard test used to determine a transmission fluid’s oxidation resistance, showed that Signature Series contained 83 percent of its original oxidation inhibitors, proving its long-lasting resistance to thermal breakdown. The graph below shows that AMSOIL ATF continued to offer reserve protection against heat after 180,000 miles of severe service.

Reserve protection against heat after 180,000 miles

AMSOIL Signature Series Synthetic ATF continues to have reserve protection against heat after 180,000 miles of severe service.
AMSOIL Signature Series ATF continued to provide reserve protection against heat after 180,000 severe-service miles (289,700 km).

Highest rating in FZG Gear Wear Test

What does AMSOIL reserve protection mean to vehicle life?

Varying speeds and loads, like those experienced by the Las Vegas taxi cabs, cause torque multiplication and extreme stress on gears and bearings. AMSOIL formulated Signature Series Synthetic ATF with high film strength and premium anti-wear/extreme-pressure additives to help prevent wear during tortuous service. Did we succeed? We put our ATF to the test to find out.

Used oil from the 180,000-mile Las Vegas taxi-cab severe-service test was subjected to the industry-standard FZG Gear Wear Test, which measures a lubricating fluid’s ability to resist gear-tooth scuffing. AMSOIL Signature Series Synthetic ATF passed all 12 progressively difficult stages with no noticeable difference in wear protection between new and used fluid.

The used oil still exceeded the Ford MERCON V and Chrysler ATF+4 specifications for new fluid.

Notice in the images below that, even after 180,000 severe-service miles (289,700 km), the transmission’s valve body was clean and virtually sludge-free. The clutch plates demonstrated only trace discoloration and earned a rating of “good,” the highest possible designation for deterioration and wear.

Even after 180,000 severe-service miles, AMSOIL Signature Series Multi-Vehicle Synthetic Automatic Transmission Fluid kept the transmission’s valve body clean and virtually sludge-free.
Even after 180,000 severe-service miles (289,700 km), AMSOIL Signature Series ATF kept the transmission valve body clean and virtually sludge-free.
Clutch plates protected by AMSOIL Signature Series ATF showed only trace discoloration after 180,000 severe-service miles (289,700 km).

Outstanding friction durability

AMSOIL Signature Series Synthetic ATF is formulated with friction-modifier additives that deliver outstanding clutch-holding capacity (static friction), torque-transfer ability (dynamic friction) and anti-shudder properties (slipping torque-converter clutches).

Analysis reveals that after the 180,000-mile severe-service test (289,700 km), Signature Series Synthetic ATF provided nearly identical friction properties as new fluid for smooth, reliable shifts.

Outstanding cold-weather performance

If you live in a cold climate, performance at startup can be an issue.

Signature Series Synthetic ATF resists thickening in winter weather, allowing for fast, reliable shifts during cold starts. Its excellent low-temperature fluidity also maximizes fuel efficiency. How can that be? Unlike conventional oils, Signature Series Synthetic ATF contains no wax, which helps improve shift response, energy efficiency and warm-up times.

Reliable leak protection

Formulated with seal conditioners, Signature Series Synthetic ATF helps prevent seals and gaskets from drying out and cracking, reducing the risk of fluid leaks.

Extended drain intervals for severe-service vehicles

Because Signature Series Synthetic ATF resists oxidation and shearing, vehicles used for severe service can double the OEM’s recommended severe-service drain interval, saving you time and money.

AMSOIL Multi-Vehicle Signature Series Automatic Transmission Fluid is the best ATF on the market.

Easy-pack design

Sometimes packaging is more than window dressing. The innovative AMSOIL easy-pack flexible-package design promotes less waste and easier fills, especially as fill ports become harder to access. As one customer put it, the easy-pack is a “game-changer” by eliminating the mess and waste that occurs with traditional ATF packaging.

Check out this video to see how the easy-pack can make your fluid changes easier and less messy.

The best ATF is AMSOIL Signature Series

When you add it all up, we think it’s clear that AMSOIL Signature Series Synthetic Automatic Transmission Fluid is the best transmission fluid on the market. It delivers optimum performance and protection for your vehicle’s transmission.