Dex-Cool® GM's Extended Life, Carboxylate Inhibited Engine Coolant

The introduction of Texaco's European style carboxylate inhibited ethylene glycol based coolant by GM in 1995 stirred a vigorous debate and precipitated the most research activity that the coolant industry has seen in decades as other companies worked to respond.

In 1995 GM began using a carboxylate-inhibited ethylene glycol coolant known as DEX-COOL®.

Goodwrench Dex-Cool

GM tested Dex-Cool extensively, and found that it could provide GM customers with improved reliability and reduced maintenance in many cases than traditional phosphate-silicate coolants such as GM 6043 type. Convinced of the overall advantages, GM phased in Dex-Cool in 1995 and 1996, with Saturn being the last to convert.

Since then, the product has been attacked at every opportunity by competitors who stand to benefit from its failure. Unfortunately, application of the technology in the American market has exposed it to some negative experiences.

Overall, GM is pleased with their decision and intends to continue to use Dex-Cool for the foreseeable future.

GM recommends and represents that Dex-Cool can serve for up to 5 years or 150,000 miles, whichever comes first. To benefit from this service interval, it is important to maintain the cooling system only with carboxylate technologies similar to Dex-Cool.

In addition to the GM brand, Texaco Havoline, Prestone Extended Life 5/150, Zerex Extreme Life and Cel-Cool should be very compatible. Dex-Cool contains a mixture of ethylene glycol inhibited with 2-ethyl hexanoic acid, sebacic acid and tolyltriazole. It contains no benzoate, nitrite, nitrate, silicate, or phosphate. The products above are very similar and consistent with that approach.

The best documented negative issue involves light trucks with 4.3 liter engines that have developed brown coolant from corrosion. A technical service bulletin was published to GM dealers regarding this problem. Someone transcribed it to the web, and the transcription can be read at:

In general, used as directed this is a capable technology.

The key to this, and other new extended life formulations is proper maintenance. That means keeping the coolant system correctly filled and using the same or very similar and compatible products.