AMSOIL SAE 50 Long Life 100% Synthetic Transmission Oil

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AMSOIL SAE 50 Long-Life 100% Synthetic Transmission Oil

AMSOIL SAE 50 Long-Life 100% Synthetic Transmission Oil (FTF) is a heavy-duty monograde SAE 50 fluid engineered for non-synchronized and synchronized manual transmissions in Class 7 and Class 8 line-haul tractors. Built on synthetic base oils and a long-life additive system, the formula targets fleets running Eaton, Eaton Fuller, Roadranger, Mack, ZF, Navistar, and Meritor manual gearboxes that demand a 500,000-mile, five-year drain interval under high-torque, high-load duty cycles.

Shear-stable wear protection through 500,000 miles of line-haul service

The synthetic base oils withstand the gear-mesh pressures and clutch loads of high-torque, high-horsepower over-the-road trucks. The fluid resists viscosity loss from mechanical shear, holding film thickness on countershaft bearings, mainshaft gears, and synchro friction surfaces. A 60-Hour KRL shear test (CEC L-45-A-99) recorded a Vk100 change of -4.97 percent, consistent with the shear stability expected of a long-life Class 8 truck transmission oil.

Real-world testing placed FTF in line-haul tractors and ran them past the 500,000-mile mark before teardown. A calibrated ASTM rater inspected the gear train. Mainshaft gears and synchro friction material showed minimal wear, and the output seal retained 100 percent of its grease with no observable leakage. The Four-Ball Wear Test (ASTM D4172, 75 C, 1200 rpm, 40 kg, 1 hr) supports this field result with a 0.38 mm wear scar.

Cold-start shifts and high-temperature stability across the duty cycle

A Viscosity Index of 142 (ASTM D2270) means a smaller change in fluid thickness from cold mornings to fully heat-soaked operation than a typical conventional SAE 50 trans oil. At negative 40 C, Brookfield Viscosity (ASTM D2983) measures 117,483 cP, supporting easier first-shifts and reduced gear drag on cold starts in northern fleets. Pour Point sits at negative 42 C / negative 44 F (ASTM D97).

At the hot end, Flash Point of 226 C / 439 F and Fire Point of 254 C / 489 F (ASTM D92) reflect the thermal margin built into the synthetic chemistry. The base oil resists oxidation and sludge formation at the high sump temperatures common in long-pull and grade-pull duty, helping mainshaft and countershaft surfaces stay clean across an extended drain.

Foam control in churning gear sets

Open helical gear stacks whip air into the fluid, and when those bubbles collapse between meshing teeth, metal-to-metal contact, and accelerated wear can follow. The foam additive system in FTF returns 0/0, 0/0, 0/0 in the ASTM D892 Foam Tendency test, indicating no measurable foam tendency or stability across the three test sequences. That keeps a continuous lubricating film on synchro cones and gear flanks even at high mainshaft speeds.

Seal compatibility and yellow-metal protection

The formula is engineered for compatibility with the elastomer seals used in Eaton, Mack, and ZF heavy-duty truck transmissions, helping prevent shaft-seal leaks and reducing seal hardening that drives end-of-service-life weeping. Copper Corrosion of 1B (ASTM D130, 121 C, 3 hr) confirms low aggressiveness toward the brass and bronze synchro components and oil-pump bushings used inside Class 8 manual gearboxes.

OEM and industry specifications

FTF is approved or recommended against the heavy-duty Class 8 manual transmission specs that fleet maintenance shops source against, including Eaton PS-164 Rev. 7 (the long-life synthetic spec used by Eaton Fuller and Roadranger gearboxes), Mack TO-A Plus, Meritor 0-81, ZF Freedomline, Navistar / International TMS 6816, Rockwell / Eaton / Fuller CD-50 (PS-081), and API GL-1 and MT-1.

Recommended applications and service intervals

FTF is intended for SAE 50 manual transmissions in heavy-duty equipment, line-haul tractors, vocational trucks, and commercial vehicles where the OEM calls for a synthetic SAE 50 long-life transmission oil.

• Manual transmissions specifying Eaton PS-164 Rev. 7, Rockwell / Eaton / Fuller CD-50 (PS-081), Mack TO-A Plus, Navistar / International TMS 6816, ZF Freedomline, Meritor 0-81, or API GL-1 and MT-1.
• Drain interval: follow the OEM drain interval for synthetic transmission oil up to 500,000 miles or five years, whichever comes first.
• Not for use in automatic transmissions (use a TES-rated synthetic ATF such as AMSOIL Torque-Drive for Allison units), hypoid differentials, or wet-clutch motorcycle transmissions.
• For trucks operated outside the US and Canada, confirm OEM specification application match with the AMSOIL Vehicle Lookup Guide before ordering.

Pair the fluid with a clean transmission oil filter at every drain. Do not mix with conventional 90-grade gear oils or non-approved trans fluids. Aftermarket additives are not required and may compromise the long-life balance of the formula.

Typical technical properties

Order AMSOIL SAE 50 Long-Life 100% Synthetic Transmission Oil

FTF is stocked in six pack sizes for owner-operators, fleet shops, and heavy-duty maintenance accounts: gallon jug (FTF1G-EA), case of four gallon jugs (FTF1G-CA), 5-gallon pail (FTF05-EA), 16-gallon keg (FTF16-EA), 55-gallon drum (FTF55-EA), and 275-gallon tote (FTF27-EA). Every order is backed by the AMSOIL Limited Warranty. Use the AMSOIL Vehicle Lookup Guide to confirm the SAE 50 long-life spec for the truck before ordering, and review the AMSOIL Manual Transmission Fluid Guide for application notes on Class 8 gearboxes, GL-4 vs GL-5, and synchromesh fluids. Order Now.

Frequently asked questions