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In order to extend the oil drain interval and to prolong the engine service life, we have investigated the effects of engine load and wear on heavy-duty diesel engine oil deterioration and oil filter plugging. Furthermore, effects of oil quality on oil deterioration has also been studied. We have found in this study that the increase of blow-by gas flow due to excessive wear of engine components causes severe nitro-oxidation in heavy-duty diesel engines at a high engine load conditions similar to that observed in gasoline engines. The nitro-oxidation of engine oil also causes filter plugging. From the oils tested, the high ash oil showed better anti-nitro-oxidation performance than those with low ash.

New double-lip and dual-lip crankshaft seals for heavy duty diesel engines have been developed. The very low radial-load, double-lip design, incorporating a helix pattern, has been adapted for high speed (30 m/s) application. In this development, we established that the seal speed limit was reached when lip coking was generated due to breakdown of the oil. A bonded dual-lip seal, which can endure speeds above 20 m/s, has been developed by adopting a unique ventilating system to release the negative pressure between the two lips. From this development, a new seal design concept involving PV values has been established.