For many years coolant has been maintained and coolant life extended for heavy duty vehicles by using periodic additions of supplemental coolant additives (SCAs) and, in many cases, use of on-board by-pass nitration of the coolant. This concept has now been applied to light duty vehicles using a system consisting of coolant testing, off board full flow coolant nitration, and SCA addition to the coolant. In this manner, coolant life in light duty vehicles may be safely extended.

The system used to maintain and extend the life of the coolant is described. Glassware, bench, and simulated service testing data are reported, which support this approach.