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The effect of phosphorus concentration in gasoline engine oils on the valve train wear was experimentally investigated by using the JASO M328-91 3A valve train wear (3A-VTW) test method. The phosphorus concentration is determined proportionally to the amount of zinc dithiophosphate (ZDDP), which is formulated as both antiwear agent and antioxidant. Lower concentrations of ZDDP generally bring about larger wear in the valve train. However, it was found from the experiments that valve train wear remained low despite a decrease of phosphorus concentration when secondary ZDDPs with short alkyl chain together with appropriate ashless dispersants were selected. Since adsorptivity of secondary ZDDPs with short alkyl chain lengths onto rubbing metal surfaces is higher than that of primary types, the secondary types give excellent antiwear characteristics.

This paper describes lubricant technology which helps to prevent intake valve deposit (IVD) formation for use with conventional gasolines without detergents, as well as the IVD evaluation method used in testing. The FED 3462 method was modified to establish a new panel coking test method, with excellent correlation with the engine stand IVD test, for the quantitative evaluation of IVD. Tests have shown that IVD increases when the volatility of base oils becomes higher due to condensation and polymerization of engine oil additives. Furthermore, viscosity index improvers, metallic detergents and ashless dispersants have considerable effect on IVD formation. Based on various experiments, the authors have established a formulation technology for engine oils to lower IVD, which they incorporated in two newly formulated SG oils with lower IVD than conventional 5W-30 SG oil.

Fuel economy is one of the most important performance features for modern engine oils. For some time now, fuel efficient engine oils (called Energy Conserving II or EC-II) have been available in the marketplace. However, the performance of EC-II oils is only 2.7% Equivalent Fuel Economy Improvement (EFEI) as measured by the ASTM Sequence VI Engine Test. To meet future industry needs, more fuel efficient engine oils are desirable. In order to achieve this, a study of highly fuel efficient engine oils was initiated. An initial target of 3.9% EFEI was selected and several candidate oils were evaluated, some of which exceeded this target. The oils were evaluated using a chassis dynamometer using the U. S. EPA mode. The test results may be summarized: 5W-30 Prototype Oil containing MoDTC showed between 1.6 and 2.6% better fuel economy than conventional 5W-30 and 10W-30 EC-II oils. There was an optimum viscosity for maximum fuel economy using the EPA testing mode.

The purposes of this paper are to develop a new laboratory oxidation stability testing method and to clarify factors relative to the viscosity increase of engine oil. Polymerized products, obtained from the oil after a JASO M333-93 engine test, were found to consist mainly of carboxyl, nitrate and nitro compounds and to increase the oil viscosity. A good similarity between the JASO M333-93 test and the laboratory simulation test was found for the polymerized products. The products were obtained not by heating oil only in air but by heating oil while supplying a synthetic blowby gas consisting of fuel pyrolysis products, NO, SO2 and air. The laboratory test has also revealed that the viscosity increase depends on oil quality, organic Fe content and hydrocarbon composition in the fuel. Moreover, it has been found that blowby gas and organic Fe accelerate ZnDTP consumption and that aromatics concentration in the fuel correlates with the viscosity increase of oil.

The relative oxidation stability of two fully formulated engine oils was compared in three testing methods by following the increase in kinematic viscosity of the oil. The purpose of the study was to determine the cause of the completely opposite ranking of the oxidation stability of the two oils that was observed in the ASTM Sequence IIIE engine test and the JASO M333 93 engine test and to determine the degree of correlation the two engine tests had with the field. The study consisted of laboratory oxidation testing, engine testing and taxi field testing to cover the range of conditions from controlled oxidation to actual driving conditions.

It has been reported that engine oils containing magnesium detergents gel under special conditions. The authors have previously reported on the mechanism by which magnesium detergents form needle crystals, which is the main cause of the gelation[1]. For this article, the authors conducted tests in actual vehicles using several types of engine oils containing magnesium detergents, including oils for which gelation problems have been reported in the market. The gelation was reproduced, and the test oils were ranked by their propensity to gel. In addition, a laboratory test method was used in which water and CO2 were mixed into engine oil under controlled conditions, then left stored in a bottle for twenty days, after which the kinematic viscosity and the quantity of insolubles of the mixture were measured. The study demonstrated the correlation between the laboratory test method and the actual vehicle tests.