In 1995, a universal “fully formulated” antifreeze/coolant specification was published for the first time in The Maintenance Council (TMC) Recommended Practices (RP) 329 and 330. It was the intent of TMC to provide a coolant that could be used in both automotive light-duty engines and heavy-duty diesel engines. This simple, one-step coolant would allow fleet managers to decrease maintenance while complying with OEM warranty requirements. In addition, fleet managers would have only one coolant to inventory. Extensive data have been presented by various authors and are recorded in the literature regarding the application of this type of coolant in heavy-duty diesel engines. Herein are reported the positive results and documentation of the successful extended service interval (ESI) application of this coolant in light-duty automobile engines, complementing the heavy-duty performance database. Vehicles from the “Big Three” American car manufacturers were operated for a distance exceeding 100 000 km (62 000 miles) with excellent experience. This paper reports the test parameters, test methods, test data and concludes that both TMC RP-329 and RP-330 compliant, phosphate-free low-silicate coolants offer ESI performance for light-duty as well as heavy-duty applications.
The data reported in this paper are derived from a controlled ESI study. The data compare the behavior of a nitrite/borate/low-silicate, low total dissolved solids (TDS) inhibitor technology in ethylene glycol and in propylene glycol coolants. Both laboratory and fleet data from six cars, powered with different makes of light-duty gasoline engines and cooled with two different types of aqueous glycol coolants for a distance exceeding 100 000 km (62 000 miles), are reported. Data include chemical depletion rates, periodic coolant chemical analyses, coolant use and makeup statistics, and engine/cooling system reliability experience. The engines were completely disassembled both at the inception and at the conclusion of the test, allowing for thorough inspection.