:In the late 1980s engine coolant recycling technologies were developed in response to a temporary but significant increase in the cost of ethylene glycol. Among these technologies was the adaptation of reverse osmosis water desalination processes by Stanadyne Automotive Corp.1 The technical paper describing the reverse osmosis (R/O) technology reports that the process efficiently recovers ethylene glycol and water in a sufficiently pure state to allow its use as a base fluid to reblend into engine coolant. Data generated in standard ASTM bench tests has demonstrated the capability of properly reinhibited R/O recycled engine coolant (ROREC) to comply with the performance requirements of accepted SAE, TMC, ASTM and OEM specifications. The technology has been applied commercially and this paper reports the operating experience of 15 users in Texas and California with diverse service applications. The experience has been very good. The data supports conclusions that users of ROREC experience engine and cooling system reliability and maintenance equal to or better than their earlier, traditional coolant maintenance programs.