Compatibility Testing of Multi-Vehicle Coolant Chemistries

Abstract Multi-vehicle or universal coolants, or both, have been introduced into the marketplace to satisfy the wishes of mass merchandisers, automotive garage and repair shops, quick oil change establishments, and the general public for a convenient single coolant for use in the myriad makes and models of vehicles. Universal coolants are recommended for top off, as well as complete drain and fill of the customer’s cooling system, regardless of the color or inhibitor chemistry of coolant already in use. Coolant mixing, and potential compatibility issues, will result for the top-off scenario, but may also be of concern following coolant system flush-and-fill. However, there are currently no standard compatibility tests to define satisfactory compatibility when coolants of different chemistry are mixed. Previous work to establish compatibility of coolant mixtures documents that potential coolant deterioration of the corrosion protection may occur in the ASTM D 4340 [1] Aluminum Heat-Rejection Test when mixing coolants with different additive chemistries. Compatibility testing has been conducted on various universal coolants with traditional high silicate, traditional low silicate, hybrid (phosphate free), hybrid (phosphated), and OAT-only technologies. This paper provides results of the coolant compatibility tests and correlation of coolant chemistry with coolant performance in these tests.