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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.

Emissions regulations for 2007 will likely require engine manufacturers to use a diesel particulate filter (DPF) to meet particulate matter (PM) emission requirements. With the lower operating temperatures of light-duty diesel engines, some form of catalyst will be required to facilitate oxidation of accumulated soot PM to regenerate the DPF. This catalyst can either be permanently applied to the filter substrate in the manufacturing process, or be continuously delivered via the diesel fuel. In this study we examined the impact of using both forms of catalyst. A recently published study of the fuel-borne catalyst additive MMT [1] (Methylcyclopentadienyl Manganese Tricarbonyl), reviewed the performance of MMT in conjunction with an uncatalyzed DPF [2].