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This paper describes development of a full-scale laboratory truck axle test used to predict the field performance of gear lubricants in heavy truck use. The relationship between laboratory results and known field performance will be described, as will a unique way of analyzing laboratory results. Data will also be presented which will show the laboratory test to be both repeatable and reproducible. Finally, data will be presented which shows lubricant additive type to play a vital role in defining field performance.

A program was conducted to develop an engine configuration and lubricant recommendation which would allow a 16,000 mile maintenance period. The program included an engine oil specification based on a multicylinder engine test, lube oil filters, coolant conditioner, cooling system modification, and increased sump capacity. Field tests were conducted. The Mack Extended Service Interval (ESI) system was developed as the result of this program.

Controlled laboratory engine tests produced a correlation between the rates of viscosity and oxidation increase and the increase in engine bmep. A multicylinder turbocharged engine test procedure was developed which correlated with field experience of known lubricants. The Mack EO-G oil recommendation was based on results obtained by evaluating representative oils of different additive levels by this test procedure.

In an ongoing effort to further improve engine durability, effects on ring wear of various engine operating variables were measured utilizing a radioactive wear test, Due to findings in this wear testing, developments were initiated in air filtration, fluid filtration and oil quality level. Implementation of these changes has improved engine durability.

A full-scale test procedure was developed utilizing the Mack differential power divider for the evaluation of gear lubricants. Test results indicate the superiority of MIL-L-2105B gear lubricants for heavy-duty rear axle carrier lubrication.

To establish a criteria for engine oil requirements for Mack diesel engines, a program was conducted to establish a specification based on the use of a production multicylinder engine. Laboratory engine tests were supplemented by field tests to assure correlation. Subsequently modifications were made to the engine test procedures to accommodate modifications in engines being marketed. Oil monitoring and oil analysis programs were also implemented to further assist in assuring adequate engine lubrication.

Field experience, together with engine laboratory testing, indicated the need for upgrading of Mack's diesel engine lubricant specifications. Field testing and laboratory testing indicated the superiority of several of the newer oil formulations for the Mack engine requirements. The newer type multi-viscosity oils were found to be particularly suited. A modified multi-cylinder engine test (T-5) was developed together with an oil specification based on the use of this test procedure (EO-J).