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Considerable development effort has shown that conventional diesel engine lubricating oil specifications do not define the needs for acceptable injector life in methanol-fueled, two-stroke cycle diesel engines. A cooperative program was undertaken to formulate an engine oil-fuel additive system which was aimed at improving performance with methanol fueling. The performance feature of greatest concern was injector tip plugging. A Taguchi matrix using a 100 hour engine test was designed around an engine oil formulation which had performed well in a 500 hour engine test using a simulated urban bus cycle. Parameters investigated included: detergent level and type, dispersant choice, and zinc dithiophosphate level. In addition, the influence of a supplemental fuel additive was assessed. Analysis of the Taguchi Matrix data shows the fuel additive to have the most dramatic beneficial influence on maintaining injector performance.

The Environmental Protection Agency will require a reduction in U.S. diesel particulate standards in 1991. To comply with this, the OEM's must modify engine design and ask petroleum refiners to reduce fuel sulfur levels to less than 0.05%. This reduction could have a dramatic impact on an engine's lubricant and possibly its performance. The durability and particulate emission stability of new engines designed to use low sulfur fuel should be related to lubricant performance and protection. Performance with low sulfur fuel must also be acceptable with equipment in service today. Laboratory evaluations of lubricant performance in current equipment were conducted with the Caterpillar 1G2 and various multicylinder diesel tests used for API CE certification. Performance differences attributable to both fuel sulfur and lubricant formulation variations have been identified and will be discussed.

A measurable incidence of driver complaints about vehicle driveability has occurred in certain imported passenger cars. Critical engines are higher specific output, lean burn designs that are sensitive to deposits formed on intake valves. U.S. engines are trending toward similar” designs but have not yet been tuned as close to the lean limit of combustion. It is reasoned that the continuing trend toward more precise management of air fuel ratio results in engines much less tolerant of deposits throughout the fuel metering and induction system. Consequently, more effective additive systems to control induction system deposits have been developed. Discussed in this paper are the interrelationships of fuel composition and engine configurations. Results of these continuing studies are helping to define the more important fuel and additive parameters for deposit control in various engines.

The development of engine oil specifications in North America, Europe and Japan has resulted in a proliferation of performance tests of increasing complexity and cost. At the same time, the transportation industry is becoming more international with vehicle populations of mixed national origin the rule, rather than the exception. In this context, regional specification writing bodies are making efforts to rationalize their own specifications and to enter into dialogue with each other. Central to any attempt at rationalization, regionally or internationally, is the availability of high-quality reference oils. Data on two formulations (a passenger car motor oil and a heavy-duty engine oil) which have met major requirements of North American, European and Japanese engine builders are presented.

Multifunctional or universal lubricating oils which service both gasoline and diesel engines have gained widespread commercial acceptance. Since 1970, numerous changes and additions have altered the performance tests and specifications which define the quality of these lubricants. New parameters include single cylinder and multicylinder diesel engine testing, valve train wear protection, clutch plate friction retention, extended drain interval and lubricant related fuel economy. In response to these requirements, new additive systems were developed. This paper discusses observed base oil-additive-engine test interactions and compares the performance of one of these additive systems to that of the old.

Studies of selected automotive gear lubricants in heavy truck tandem axles and transmissions have revealed improvements in fuel economy associated with the viscosity of lubricants tested (grades 75W, 75W-90, and 80W-140). The testing included a heavy truck on-highway fleet test and test track operation. Standard laboratory gear tests on light viscosity monograde (SAE 75W) oils indicate that oils of this type may be deficient in EP protection. Combined observations show that there may be a critical balance between axle lubricant fuel economy benefits and axle durability in field service.

It has been recognized for many years that multipurpose axle lubricants give rise to much higher axle break-in temperatures than lead-soap, active-sulfur or sulfur-chlorine-lead lubricants. Evaluation of differences in axle lubricant break-in temperature between the various multipurpose gear lubricants has been complicated by lack of repeatability and reproducibility. The work described in this paper shows that one of the most important variables affecting axle break-in temperature, under the conditions of the test technique used, was torsional axle preload and that control of dimensional preload in itself is not sufficient to ensure good test repeatability. The test technique described here has been used to evaluate the axle lubricant break-in temperature properties of several sulfur-phosphorus multipurpose gear lubricants.