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The current trend within the automotive industry is aimed towards reducing the cost of vehicle ownership. A major area of focus is lengthening recommended vehicle service intervals. Automotive technology has now advanced to the point where, for many of today's vehicles, the first mechanical “tune-up” is not required until the vehicle has reached 100,000 miles. On the other hand, engine oil servicing is still recommended at intervals in the range of 3,000 to 7,500 miles in the North American market. Extension of oil change interval recommendations beyond 15,000 miles is now being discussed within the international automotive industry. This paper documents the development and testing of new synthetic engine oil technology under extended service intervals of up to 25,000 miles or three years.

Unique performance advantages for polyalphaolefin (PAO) based synthetic engine oils have been documented since the mid-70's (1). The superior performance of these lubricants led the industry to develop improved mineral-based lubricants, including those produced by isomerization of waxes. Recently, an extensive research project was initiated to further enhance the performance advantages of PAO-based synthetic engine oils compared to highly refined mineral oils. A new generation of synthetic lubricant was developed delivering significantly improved performance in all areas. Although the development took place before the introduction of the API “SH” engine oil category, this new synthetic engine oil technology far exceeds API “SH” requirements as well as the API “CD” diesel performance specification. This paper discusses the standard and extended-length (U.

Outstanding overall engine performance has been obtained by formulating automotive engine lubricants with synthetic base stocks. This paper summarizes the performance features of an optimized SAE 10w-30 synthetic passenger car engine oil. Comparisons to premium mineral oil-based products are made in areas of fuel economy, low-temperature cranking, high-temperature deposition, antiwear performance, quality reserve capability, and oil consumption control. Supporting data are shown from tests involving U.S., European, and Japanese vehicles.

Utilizing extensive synthesized hydrocarbon fluid (SHF) technology, a superior quality light viscosity automotive engine oil has been developed providing optimized engine performance. This product has been shown to provide significant fuel economy benefits while maintaining excellent performance in the areas of oil economy, engine cleanliness and wear protection. In the past, this level of performance has not been possible using conventionally refined mineral oils. The superior performance of this product is extensively documented in U.S. and European laboratory engine, chassis dynamometer and field tests. Fuel economy benefits are shown for a wide variety of vehicles under a number of test conditions including both chassis dynamometer and over-the-road field testing. Additionally, the performance reserve capabilities of this product are demonstrated by the results of extended drain field tests and extended duration API sequence engine tests.

Formulation of current automotive diesel engine oils is partially guided by military and engine builders ’ requirements and specifications. The roles of both the base stock and chemical additives are important in handling contaminants and debris which may cause excessive deposits and wear. Future changes in diesel lubricants will be somewhat dependent on engine design changes. The future of cross-graded oils in current and future engines is very promising.

The development of extreme pressure and limited slip automotive gear oils requires care in the selection of base stocks and additives in order to achieve the desired balance of performance properties. Considerations involved in selection of extreme pressure agents, corrosion inhibitors, and friction modifiers are enumerated. Of particular interest is the interference of many corrosion inhibitors and friction modifiers with the desirable gear protection properties. Tests are described for use in evaluating the additives, and performance properties of fully formulated oils are shown. The need for a special lubricant for limited slip axles is described.

A comprehensive study was conducted to evaluate additives for their ability to reduce the coefficient of friction of synthetic engine oils using a laboratory bench test apparatus. A class of additives was identified that also proved effective in providing fuel economy benefits when tested in vehicle dynamometer evaluations. Additional investigations using the proposed ASTM Five Car Energy Conserving Engine Oil Test Procedure confirmed the fuel saving performance of this specific additive class. This paper also discusses overall engine performance of synthetic engine oils formulated using this unique type of friction reducing additive. A full series of API SF/CC/CD quality level sequence tests, including critical extended length evaluations, was performed and excellent performance was demonstrated.

Two-cycle gasoline engines offer some unusual problems in lubricant development. Because of the one-pass lubrication system employed, the lubricant affects combustion and the fuel system in general to a much greater extent than in four-cycle engines. This paper discusses the various aspects of lubricant composition as related to engine operations. Data are presented which show those factors of base stock composition and of various additive classes which affect the piston cleanliness, exhaust system deposits, wear, and spark, plug operation of two-cycle gasoline engines.

Turbocharging of gasoline-powered passenger car engines, to provide improved performance while maintaining good overall fuel economy, has been adopted by some U.S. and overseas builders. The high temperatures encountered in turbochargers can seriously affect the engine oil life. Under certain severe operating conditions excessive oil degradation deposits can be formed in the turbochargers which can lead to bearing failure. A vehicle chassis-rolls test procedure was developed to evaluate lubricant composition effects on turbocharger deposits and bearing condition. Evaluations of a number of different engine oils have demonstrated superior performance for one class of synthetic oil over high-quality mineral oils in lubricating the high-temperature areas of passenger car turbochargers.

Discussion of the rotary-combustion engine's history, operation, and lubrication illustrates the role of various quality level engine oils in providing the necessary functions of engine seal wear protection, bearing lubrication, rotor cooling, and overall combustion chamber area cleanliness. Specific examples of current quality and experimental-type engine oil influence on overall engine durability, including seal and housing surface wear, are cited for various engine designs. Data evaluating lube oil effects on engine cleanliness and oil consumption characteristics are also discussed. Analysis of used oil from a number of test engines is presented showing the rotary-combustion engine to yield oil deterioration typical of current piston engines.

Recent advances in polymeric Viscosity Index improver technology have led to the development of premium quality, broadly crossgraded passenger car engine lubricants with unique physical properties. “True” SAE 10W-40 products can be made, where measured SAE 10W performance is obtained together with shear stability characteristics which enable the oil to remain in the SAE 40 viscosity range even after service in normal passenger car engines. “True” SAE 10W-40 lubricants provide oil economy characteristics significantly superior to those afforded by conventional SAE 10W-30 and SAE 10W-40 oils, and equal the performance of available SAE 20W-50 oils, while also offering excellent low temperature cranking and starting ability. Positive benefits of improved engine hot starting capability and reduced engine noise levels are also provided.

Two synthesized commercial engine oils have been developed and extensively evaluated to document a number of unique performance benefits. The benefits include significant fuel savings in heavy-duty diesel truck engines, excellent low temperature fluidity, engine cleanliness and antiwear protection, extended drain capability, and good oil economy. The results of standard and double-length laboratory engine tests, chassis rolls tests and confirming field tests are discussed in the paper.

A new class of synthetic fluids has been developed with specific physical and chemical properties, which can be used to formulate automotive engine lubricants with a performance range far exceeding that obtainable with conventional mineral-oil-based lubricants. New, unique synthetic engine lubricants are described that provide improved low-temperature fluidity and cold-starting performance, better high-temperature stability and engine cleanliness, outstanding viscosity stability, reduced oil consumption, better oil pressure retention, and reduction of engine wear. The superiority of these new synthetic lubricants is documented with results of evaluations conducted in a wide range of engines and vehicles using standard and newly developed test procedures. Testing under severe rally and field conditions is also discussed.

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.

ENGINE noise has become an increasing problem with the higher and higher compression ratios of present-day automotive engines. Because fuel octane number cannot be raised indefinitely, the problem is one of engine design and selection of crankcase lubricating oils and gasoline formulations, the authors think. This paper describes investigations into the cause of spark knock, wild ping, rumble, and the added problem of hot-spot surface ignition (which also intensifies as compression ratios increase). The authors have found gasolines with phosphorous additives, used with properly formulated multiviscosity lubricating oils, provide a partial answer to the problem of engine rumble. The authors conclude that very exact tailoring of fuels, lubricants, additives, and engines will be necessary to prevent engine noise if compression ratios continue to rise.