Future U.S. Army low heat rejection (LHR) diesel engines will operate with oil sump temperatures higher than 350°F and cylinder wall temperatures (at the top ring reversal position) which may reach 1100°F. None of the synthetic lubricants which have previously been evaluated in LHR engine prototypes are able to function for long in such a severe thermal/oxidative environment.
Work is being performed for the U.S. Army on development and evaluation of new high temperature diesel engine lubricants. The most significant result of this work has been the development of a low cost liquid lubricant which exhibits high temperature performance superior to the best previously developed LHR engine lubricant in all respects: deposit-forming tendencies, stable life under high temperature oxidative conditions, and friction and wear properties. The scientific considerations employed in development of this lubricant, and the results of laboratory and engine tests on this and other lubricant candidates, are reported here.