Short answer
TES-295 and TES-668 are Allison Transmission fluid specifications for its on-highway automatic transmissions. Allison announced TES-668 in September 2020, with fluids on the market from January 2021, and says TES-668 fluids are backward compatible with any transmission that requires TES-295. TES-389 is an older, lower-tier Allison specification that does not carry the same extended drain and filter intervals.
What TES means and who uses it
TES stands for Transmission Equipment Specification. Allison writes these documents for the fluids used in its automatic transmissions, which are common in pickups, delivery trucks, school buses, refuse trucks, fire apparatus and motorhomes.
Allison maintains an approved-fluids list on its website. A fluid is Allison approved for a TES specification only if it appears on that list; a label saying a fluid is “for Allison applications” is not the same thing.
TES-295: the long-running synthetic spec
TES-295 was for many years Allison’s top on-highway fluid specification and is associated with Allison’s extended drain and filter intervals. Allison still lists TES-295 approved fluids for its 1000, 2000, 3000 and 4000 Series and H 40/50 EP products, while encouraging customers to consider TES-668 at their next service.
TES-668: the current recommendation
Allison announced TES-668 on September 29, 2020. According to Allison’s announcement as reported in the trade press, TES-668 fluids offer improved oxidative stability, antiwear performance and friction modifier durability compared with legacy TES-295 fluids, aimed at keeping shift quality consistent as the fluid ages.
Allison’s current fluid pages recommend TES-668 approved fluids for its 1000, 2000, 3000 and 4000 Series, H 40/50 EP, and eGen Flex and eGen Power on-highway products. Allison also states that TES-668 fluids can be used in any transmission that requires TES-295.
TES-389, Dexron VI and C-4
TES-389 fluids may be used in traditional on-highway Allison products, but Allison dealer guidance notes they don’t provide the same drain or filter change intervals as TES-668 or TES-295 approved fluids. The same guidance says C-4 fluids and Dexron VI are no longer recommended in any commercial on-highway Allison transmission.
Off-highway Allison transmissions have their own fluid recommendations. For any unit, use Allison’s operator manual and current approved-fluids list, and match drain intervals to the fluid category actually in the transmission.
Frequently asked questions
Can TES-668 fluid go in a transmission that calls for TES-295?
Allison states that TES-668 fluids are backward compatible with any transmission requiring TES-295.
Where do I find Allison approved fluids?
Allison publishes its approved-fluids lists for TES-668 and TES-295 on its website. Approval is by named product.
Does fluid choice affect Allison drain intervals?
Yes. Allison’s published intervals depend on the fluid category; TES-389 fluids do not get the extended intervals tied to TES-668 or TES-295 approved fluids.
General maintenance information. Always follow your vehicle or equipment manufacturer’s requirements and the current product data. Questions? Email [email protected].