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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.

Quality control of gasoline constituents and its effect on the Intake Valve Deposits (IVD) has become a recent issue. In this paper, the effects of gasoline and oil quality on intake valve deposits were investigated using an Intake Valve Deposit Test Bench and a Sludge Simulator. The deposit formation from the gasoline maximized at an intake valve temperature of approximately 160 °C, and the deposits formed from the engine oil were maximum at approximately 250 °C. Therefore, the contribution of the gasoline or the engine oil appears to depend on the engine conditions. The gasoline which contains MTBE or ethanol with no detergent additive slightly increases the deposition amount. The gasoline with a superior detergent significantly decreases the deposition amount even when MTBE or ethanol is blended in the gasoline. Appropriate detergent fuel additive retards the oil deterioration.