<P> Originally the DEXRON name was associated exclusively with automatic transmission fluids, later GM released DEXRON gear oils and other lubricants under the DEXRON brand . </P> <P> The original Dexron transmission fluid was introduced in 1968 . Over the years, the original Dexron was supplanted by Dexron - II, Dexron - IIE, Dexron - III, and Dexron - VI, which is the current fluid . GM has upgraded the Dexron specifications over the years; newer fluids are generally but not always backward compatible with previous fluids . Because there are still applications for which Dexron - VI either has not been proved suitable or deemed to be not necessary, there remains a market for fluids that claim to meet the earlier specifications . </P> <P> The original Dexron fluid, like its predecessor Type - A / Suffix - A, used sperm whale oil as a friction modifier . The U.S. Endangered Species Act banned the import of sperm whale oil, so the fluid had to be reformulated . </P> <P> Dexron - II was introduced in 1972 with alternative friction modifiers such as Jojoba oil . However, it caused problems with corrosion - prone solder in GM's transmission fluid coolers; accordingly, corrosion inhibitors were added to the product . The resultant fluid, released in 1975, was called Dexron - IID . However, the corrosion inhibitor made the new fluid hygroscopic, which while it was not a major problem in automatic transmissions, made Dexron IID unsuitable for other hydraulic systems in which it was commonly used . A further reformulation, to address excessive hygroscopicity, but primarily to improve low temperature performance (20,000 cP @ - 40C vs 50,000 cP @ - 40C for Dexron - IID) was named Dexron - IIE (GM Spec GM6137M). </P>

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