An Evaluation of Glycerin (Glycerol) as a Heavy Duty Engine Antifreeze/Coolant Base 2007-01-4000

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.

Results of a literature search are presented as well as recent laboratory, bench, engine/dyno, chassis/dyno and field test data pertinent to the use of glycerin as a base fluid for heavy duty engine antifreeze/coolant. The performance of glycerin is addressed in areas including:

• Heat transfer
• Corrosion protection
• Cylinder liner cavitation corrosion
• Freeze point and other physical properties
• Low temperature viscosity
• Thermal stability
• Elastomer compatibility
• Toxicity relative to ethylene glycol and propylene glycol

Finally, areas for further work are proposed.