DEXRON is the trade name for a group of technical specifications for automatic transmission fluid (ATF) created by General Motors (GM).

The automatic safety transmission was first offered as an extra-cost option by the Oldsmobile Division of GM in the fall of 1937 for their Six and Eight models.

The automatic safety transmission used the same seasonal grade of motor oil as the engine for lubrication and hydraulic functions.

This fluid was composed of a Group 1 base oil and additives to reduce oxidation, foaming, rust, corrosion, varnish, and sludge buildup.

[5] As a result, qualified GM automatic transmission fluid was made available at retailers and service garages in many places.

It is important to understand that every automatic transmission produced by any vehicle manufacturer (Oldsmobile, Cadillac, Buick, Chevrolet, Pontiac, GMC, Ford, Mercury, Lincoln, Chrysler, Dodge, Desoto, Packard, and Studebaker) used motor oil or the GM Type "A" transmission fluids from 1949 to 1958.

[10] GM continued the licensing program, allowing oil companies to produce the new Type "A" suffix "A" fluid under their own brand name.

[11] DEXRON (B) was composed of a more stable, less reactive, hydrotreated Group 1 base oil plus additives to help prevent foaming, oxidation, and damage from elevated temperatures.

Endangered Species Act banned the import of sperm whale oil, so the DEXRON (B) fluid additive package had to be reformulated.

[14][15] DEXRON-II(C) was composed of a more stable, less reactive, hydrocracked Group 2 base oil plus a revised additive package with corrosion and rust inhibitors such as jojoba oil; however, the additive package caused problems with corrosion-prone solder in a relatively small number of GM's transmission fluid coolers.

DEXRON-II(D) was composed of Group 2 base oil plus an additive package with alternative corrosion and rust inhibitors.

The automotive industry responded by changing to three typically unused transmission technologies: The 1978 introduction of the TCC led to customer complaints of a shudder while driving.

GM was first to market with Cadillac Allante's electronic-controlled transmission system, THM F-7, in 1987, followed by Chrysler and Toyota in 1988, and Ford in 1989.

This specification failed to address a number of issues concerning long-term durability, such as shear stability and fluid oxidation.

DEXRON-III (F) underwent a number of iterations in an attempt to address various shortcomings but was eventually replaced by new thinking, i.e., DEXRON-VI (J).

Engineers determined that road forces being transferred through the TCC were affecting the normal rotational fluctuations of the crankshaft and tricking the ECM into thinking there was a cylinder misfire.

universal for all automatic transmissions with and without controlled torque converter lockup clutch, the so-called GKÜB for gear-clutch-lock.

[23] The container rear label reads "Full Synthetic Automatic Transmission Fluid"; however, the base oil composition is not stated.

All DEXRON-III (H) licenses expired permanently at the end of 2011, and GM now supports only DEXRON-VI fluids for use in their older automatic transmissions.

[24] Aftermarket fluids asserted by their manufacturers to meet DEXRON-III(H) and earlier standards continue to be sold under names such as DEX/Merc.

With increasing CAFE regulations, smaller engines with very narrow torque bands were being put in vehicles with 6- and 8-speed transmissions to improve fuel economy.

DEXRON-ULV is composed of a Group 3+ base oil and additives needed for the proper operation of the 2017 and above GM 10L90 and the Ford 10R80 10-Speed rear-wheel-drive automatic transmission.

In 2016, a new fluid specification for a "DEXRON Approved" Mobil 1 Synthetic LV ATF HP was introduced in GM Technical Service Bulletin 16-NA-175.

DEXRON LV ATF HP is composed of a poly-alpha-olefin (PAO) Group IV base oil and additives developed by Afton Chemical needed for the proper operation of the 2015 and above GM 8L90 8-Speed rear-wheel drive automatic transmission.

On October 1, 2018, a special fluid specification (GMNA-9986555[27]) was introduced for a revised "DEXRON Approved" Mobil 1 Synthetic LV ATF HP.

The revision is to help correct a torque converter clutch shudder in the GM 8L90 and 8L45 automatic transmissions after a complete flush of the system.

Mobil-1 LV ATF HP is composed of a Gas to liquids (GTL) Group 3+ Base oil and additives developed by Infineum needed for the proper operation of the 2015 and above GM 8L90 and 8L45 8-Speed rear wheel drive automatic transmission.

GM Lifetime automatic transmission fluids made from higher-quality base oil and an additive package are more chemically stable, less reactive, and do not experience oxidation as easily as lower-quality fluids made from lower-quality base oil and an additive package.

Therefore, higher-quality transmission fluids can last a long time in normal driving conditions (typically 100,000 miles (160,934 km) or more).

Always consult the vehicle maintenance guide for the proper service interval for the fluid in your transmission and your driving conditions.