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During development of the General Motors rotary engine, the lubricant was recognized as important to its success because certain lubricants produced deposits which tended to stick both side and apex seals. Consequently, it was decided to develop a rotary engine-dynamometer test, using a Mazda engine, which could be used for lubricant evaluation. In an investigation using an SE engine oil with which there was rotary engine experience, engine operating variables and engine modifications were studied until the greatest amount of deposits were obtained in 100 h of testing. The most significant engine modifications were: omission of inner side seals, plugging of half the rotor bearing holes, pinning of oil seals, grinding of end and intermediate housings, and using a separate oil reservoir for the metering pump. Using this 100 h test procedure, three engine oils and five automatic transmission fluids were evaluated.

In certain types of city bus service some automatic transmission fluids can fail in less than 10,000 miles. In order to provide satisfactory transmission performance for longer mileage, improved fluids are required. An investigation was undertaken to obtain improved fluids. Fifteen different fluid formulations were evaluated in 30 city buses operated in normal service for more than 2,000,000 miles. It was determined that fluids fail because of frictional deterioration and oxidation. Based on these evaluations, only two fluids were found to be satisfactory for more than 40,000 miles; one additional fluid was satisfactory for more than 30,000 miles. The remaining 12 fluids failed in less than 20,000 miles.