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This paper describes the engine test and extended oil drain field performance of new synthetic engine oil technology developed for use in North American low-emission heavy-duty diesel engines. The resulting formulation utilizes an advanced additive system specifically tailored for synthetic base stocks which exceeds current industry and engine builder targets in critical performance tests. Use of synthetic base stocks allows the formulation of engine oils with a unique combination of performance characteristics, which include meeting SAE 5W-40 viscosity requirements for cold starting benefits while maintaining low volatility loss at high temperature for oil consumption control. In addition to meeting API CG-4, CF-4, CF-2, CF, SH and EC requirements, this technology has also demonstrated exceptional performance in extended-length diesel and gasoline engine tests. Furthermore, it has also performed very well in extended service interval field tests.

Since diesel engine oils are part of the low-emission equation, there has been stepped increases in the quality of crankcase oils with the stepped reduction in diesel exhaust emissions. The new API CG-4 oil category, was developed to address the Engine Manufacturers Association's (EMA's) needs for 1994 emission-controlled diesel engines. It also improves the quality of crankcase oils by using modern four-cycle diesel engine tests which: operate on low-sulfur diesel fuel, as used by all on-highway trucks in the U.S., have statistically defined test limits, are incorporated into the Chemical Manufacturers Association's (CMA's) rigorous code for qualification testing.

A test program has been conducted to evaluate the low-temperature cranking, pumping and starting characteristics of light and heavy duty diesel trucks using various lubricants. The low-temperature performance of oils with different SAE viscosity grades and base stock type were evaluated. Included are formulations based on conventional mineral, hydrocracked and synthetic base stocks. The results show that lower viscosity grade oils using special base stocks, in particular synthetics, demonstrate improved low-temperature cranking and pumping performance over conventional lubricants. The engine test results are compared against laboratory low-temperature flow, cranking and pumpability tests.

By controlling their molecular structure, synthesized base fluids can be produced which provide optimal properties for formulating lubricants. One of these properties is outstanding low-temperature fluidity. This paper describes a range of fully synthetic automotive lubricants, including engine oil, gear oil and automatic transmission fluid, which through the use of selected synthetic hydrocarbon fluids have shown superior properties for low-temperature operation. The low-temperature benefits of these optimized synthetic formulations compared to mineral oils are demonstrated by physical property analysis, laboratory bench tests for flow, cranking and pumpability, and full-scale vehicle cold-starting tests. These results are confirmed in low-temperature operations in commercial applications.

Synthesized passenger car engine oils have shown a wide range of performance benefits in automotive gasoline engines. These oils also satisfy the additional demands of small diesel engines used in passenger cars and light-duty vehicles. This includes the severe requirements of turbocharged passenger car diesel engines. Excellent high-temperature deposit control, wear protection and fuel economy are documented for synthetic engine oils in U.S. and European diesel engine dynamometer, chassis rolls and fleet tests operated under severe conditions. Many of the field tests were conducted with greatly extended oil drain intervals, further stressing oil quality. Test results support the outstanding passenger car diesel engine lubrication capability for optimized synthetic engine oil formulations. The performance advantages of synthetic automotive lubricants in gasoline engines have been well documented (1, 2, 3, 4, 5, 6, 7, 8)*.

Considerable activity is progressing to define lubricants with improved performance to meet the severe demands of modern automotive diesel engines. This paper discusses monograde and multigrade diesel engine oils formulated to provide superior performance with respect to ring sticking, cylinder bore polishing, oil consumption valve train wear, alkalinity retention and engine cleanliness in severe turbocharged diesel engines. These highquality diesel engine oils exceed current industry requirements and meet the severest performance specifications of major European and U.S. builders. This performance is demonstrated in single and multicylinder engine dynamometer tests including several proprietary procedures. Field testing in severe fleets under extended drain conditions confirms the superior quality of these lubricants compared to conventional diesel engine oils.

The fuel-saving capabilities of various experimental and commercial passenger car engine oils have been demonstrated in extensive studies. Lower viscosity oils and those containing friction-reducing additives have shown measurable fuel economy benefits in a wide range of laboratory and vehicle tests. Several test techniques are described for screening fuel-saving engine oils and components. Closely controlled chassis rolls and over-the-road vehicle tests are utilized to demonstrate the actual lubricant-related fuel economy benefits. Within the range of variables included in this study, reducing engine oil viscosity is the most effective way to improve fuel economy. Fuel savings realized from friction-reducing additives are relatively modest and many of the more effective materials are shown to have poor performance in standard sequence tests, particularly regarding engine wear.