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To evaluate the influence of FAME, which has poor oxidation stability, on engine oil performance, an engine test was conducted under large volumes of fuel dilution by post-injection. The test showed that detergent consumption and polymerization of FAME were accelerated in engine oil, causing a severe deterioration in piston cleanliness and sludge protection performance of engine oil.

Engine oil combined with SPZn instead of ZnDTP shows excellent total base number (TBN) retention in oxidation and NOx gas bubbling tests. The wear resistance of engine oil combined with SPZn was similar to oil combined with ZnDTP in a four-ball test. Prototype engine oils with 1.0 wt% of sulfated ash and 0.04wt%-0.09wt% of SPZn-derived phosphorus were prepared and a JASO valve train wear test was performed on them. The wear resistance of engine oil including SPZn with P = 0.09 wt% was greater than that of engine oil including ZnDTP. This result shows the possibility of reduce the phosphorus in engine oil by using SPZn.

A low sulfated ash (S.Ash) DL-1/C2 0W-30 diesel engine oil with improved fuel economy has been developed to meet the PM targets outlined in the Euro 5 emissions standards and to help achieve the voluntary European CO2 target of 140 g/km. The newly developed engine oil is an effective solution to the trilemma (triple probrem) of reliability (high detergency and high anti wear), low S.Ash, and fuel economy, achieving a fuel economy improvement of 2% and reducing CO2 emissions by 3 g/km.

The energy conserving by engine oils has been required from the viewpoint of the environmental issue. The fuel efficiency of passenger car engine oils has been improved by adding friction modifiers. However, engine oils containing friction modifiers can not be applied to 4-stroke motorcycles. Because motorcycles normally have a wet clutch system inside the crankcase and such engine oils can decrease the clutch capacity.1) ∼ 2) Therefore, it is important for motorcycle engines to investigate additives, which can increase friction coefficient on paper-based friction materials. In this study, friction coefficients of engine oils formulated with different additives such as dispersants and detergents were evaluated with a reciprocating friction tester. Several types of polybutenyl succinimides, sulfonates, phenates and salicylates were used as dispersants and detergents.

Modern formulation in a wide variety of lubricants including engine oils and transmission fluids is designed to control friction through film-forming tribochemical reactions induced by the functional additives mixtures. Although many cases on the synergistic or antagonistic effects of additives on friction have been reported, their mechanisms are poorly understood. This study focused on the influences of metallic detergents on tribochemical reactions. We examined the mechanical properties of detergent-containing lubricants confined at a single-asperity contact and their contributions to tribochemical phenomena. We found that detergents enlarged the confinement space required for generating repulsive force and shear resistance. This means that these detergents provide steric effects under nanoconfinement at interfacial contacts.

We report in this paper our newly developed technology applied to ILSAC GF-5 0W-20 engine oil that offers great fuel economy improvement over GF-4 counterpart, which is a key performance requirement of modern engine oil to reduce CO2 emissions from a vehicle. Our development strategy of the oil consisted of two elements: (1) further friction reduction under mixed and hydrodynamic lubrication conditions considering use of roller rocker arm type valve train system and (2) lowering viscosity at low temperature conditions to improve fuel economy under cold cycles. Use of roller rocker arm type valve train system has been spreading, because of its advantage of reducing mechanical friction. Unlike engine with conventional direct-acting type valve train system, lubrication condition of engine with the roller rocker arm type valve train system has higher contribution of mixed or hydrodynamic lubrication conditions rather than boundary lubrication condition.

Two-stroke engines have been normally used for power equipment such as bush cutters and lawn mowers because of their compactness and cost-performance. However, their exhaust smoke is often put in question for causing a poor working environment. Therefore, it is important to develop an environmentally friendly two-stroke engine oil. In this paper, the development of a two-stroke engine oil with low smoke performance and its evaluation results are reported. If dilution ratio of a two-stroke engine oil with gasoline is increased in order to reduce the exhaust smoke, the lubricity becomes poor because of the decrease of base oil ratio in the oil. A two-stroke engine oil that copes with both low exhaust smoke and anti-seizure performance for pistons, has been developed by using a carefully selected polymer ester. The oil showed excellent anti-seizure performance in actual engine tests.