Propylene glycol (PG) has been demonstrated to be a viable alternative to ethylene glycol (EG) as a base fluid in engine coolants using a variety of laboratory tests designed to simulate on-the-road vehicle conditions. However, actual vehicle testing has been primarily limited to heavy duty diesel applications and the specialized protocol required for high temperature desert evaluations.A light-duty propylene glycol coolant has been evaluated in a 1 year, 48,280 kilometer (30,000 mi.) test using a 15 vehicle fleet composed of compact, mid-size, and sport-utility vehicles. Mileage was accumulated at an average rate of 177 kilometers (110 mi.) per day using a combination of highway, suburban, and city driving routes. Corrosion inhibitor depletion rates and metal coupon weight loss data are presented as are photographs of cooling system components removed from the vehicles at the conclusion of the test. The results illustrate the excellent performance attainable when propylene glycol coolant is used in light-duty passenger vehicles.