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More stringent emission legislation has been a driver for changes in the design of Heavy Duty Diesel engines since the 1980s. Optimization of the combustion processes has lead to significant reductions of exhaust emission levels over the years. However, in the year 2002, diesel engines in the USA will have to meet an even more stringent set of emission requirements. Expectations are that this will force most engine builders to incorporate Exhaust Gas Recirculation (EGR). Several studies of the impact of EGR on lubricant degradation have shown increased levels of contamination with soot particles and acidic components. Both of these could lead to changes in lubricant requirements. The industry is developing a new specification for diesel engine lubricants, PC-9, using test procedures incorporating engines with EGR.

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.

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 new 998 CID V8 engine series has been developed by Mack Trucks, Inc. to supplement its line of heavy duty diesel engines. These engines, the E9 Series, are available in two configurations--a 400 bhp (298 kW) high torque rise version and a 440 bhp (328 kW) conventional torque backup version. Increased horsepower and improved fuel economy were achieved through the development of a chassis mounted charge air cooler and a new four-valve cylinder head. In addition, significant durability improvements were obtained due to the reduced thermal loadings resulting from the lower charge air temperatures. Additional noteworthy features include a new injection pump, improved lube oil system, advanced piston design, and proper selection of seals and gasket materials.

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).