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The purposes of this series of studies are to examine the characteristics of intake-valve deposits and to clarify their formation mechanism. This paper discusses the chemical compositions and physical states of the deposits on the basis of the results obtained by chemical analyses. The results indicate that the deposits mainly originate from engine oil, and suggest that the main reaction route of the deposit formation is the carbonization of oxidized engine oil. Namely, low boiling point (light) fractions in the engine oil easily evaporate from the valve surface. On the other hand, the remaining heavy fractions are subjected to deposit forming reactions. These final states are amorphous and carbonaceous aggregates. The deposit has a tendency to form in the temperature range of about 230 to 350 °C. The location of accumulating deposit depends on the valve surface temperature.

A laboratory scale simulation test method was developed to evaluate deterioration of radial lip seals of fluoroelastomer (FKM) compounds for engine crankshafts. The investigation of the collected radial lip seals of FKM compounds from the field with service up to 450,000km indicated that the only symptom of deterioration is a decrease of lip interference. This deterioration was not duplicated under conventional test conditions using an oil seal test machine because sludge build up at the seal lip caused oil leakage. However, revised test conditions make it possible to duplicate the deterioration experienced in the field. An immersion test using a radial lip seal assembled with the mating shaft was newly developed. This test method was found to be useful to evaluate deterioration of radial lip seals using FKM compounds. Oil additives affect the deterioration of lip seal materials significantly. Therefore, immersion tests of four different oils were conducted to evaluate this effect.

The lubrication properties of engine oils change in the early stage of car running and after that the oils keep a good antiwear property and a low friction coefficient even after 10,000 km running. On the other hand, the thin layer chromatography spot characteristic of ZnDTP disappeared after 2,000 km running. The reason why the antiwear property of the used engine oils was retained after decomposition of ZnDTP has been discussed. Analytical results indicated that P=S bond of the ZnDTP disappeared at a running distance of 2,000 km but P-O-C bond remained after 10,000 km running. In laboratory tests, ZnDTP decomposed by heating at a temperature of 120 °C with eliminating olefins after an induction period of 100 h. With a sample oil containing ZnDTP alone, the additive decomposed into precipitate upon heating to 135 °C for 60 h, and the antiwear property of the oil deteriorated.

Toyota participated in Formula One1 (F1) Racing from 2002 to 2009. As a result of the downturn in the world economy, various engine developments within F1 were restricted in order to reduce the cost of competing in F1. The limit on the maximum number of engines allowed has decreased year by year. Toyota focused on the engine performance deterioration due to the combustion chamber deposits. In 2009, Toyota was successful in reducing around 40% of the deterioration by making combustion chamber cleaner in cooperation with ExxonMobil. This contributed to good result of 2009 F1 season for Toyota, including two second place finishes.