Recently there has been interest by motor vehicle manufacturers in developing longer-lived automotive engine coolants with an emphasis on organic acid technology (OAT) . Paradoxically, the lifetime of conventional technology remains largely undefined. Concerns arising from the depleting nature of silicate have led to modern conservative change recommendations of 30 000 to 50 000 miles (∼48 279 to 80 464 km) .
In the present work, laboratory bench test, engine dynamometer and vehicle service data from traditional silicate, hybrid and nonsilicate coolants are compared and contrasted. A new electrochemical test is used to examine passivation kinetics on aluminum. It is shown that performance and lifetime are independent of chemistry and cannot be generalized. Examples include an American silicate coolant with excellent performance on high-heat-rejecting aluminum (80 W/cm2), European and American silicate coolants with performance defined lifetimes in excess of 300 000 miles (482 790 km), and an OAT coolant with laboratory high lead solder protection. It is concluded that the primary benefit of OAT is to meet global specifications that include chemical limitations.