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In the early years of antifreeze/coolants (1920s & 30s) glycerin saw some usage, but because of higher cost and weaker freeze point depression, it was not competitive with ethylene glycol. Glycerin is a by-product of the manufacture of biodiesel (fatty acid methyl esters) made by reacting natural vegetable or animal fats with methanol. Biodiesel fuel is becoming increasingly important and is expected to gain a large market share in the next several years. Regular diesel fuels blended with 2%, 5%, and 20% biodiesel are now commercially available. The large amount of glycerin generated from high volume usage of biodiesel fuel has resulted in this chemical becoming cost competitive with the glycols currently used in engine coolants. For this reason, and lower toxicity comparable to that of propylene glycol, glycerin deserves to be reconsidered as a base for antifreeze/coolant.

In 1991, Frank Kelley of Caterpillar wrote: “In warm climates, it is still common for water with an appropriate concentration of supplemental coolant additive (SCA) to be used in heavy duty engine systems. This practice will probably become less acceptable as engine operating temperatures increase and aluminum components find their way into applications in heavy duty diesels in the future.” 1* That time has now come. Furthermore, as exhaust gas recirculation (EGR) becomes prevalent in 2002 engine designs, additional heat load will be transferred to the cooling system due to cooling the recirculated exhaust gas before its introduction to the air intake. This will further increase the need for the use of antifreeze/coolant due to the need for higher radiator top tank temperatures to handle the greater coolant heat load. Additionally, use of antifreeze coolants in older engines is very beneficial even though coolant temperatures may not be high.