ガソリン機関用潤滑油の低温スラッジ生成に関する一考察

抄録

It is widely known that the composition of blowby and crankcase gases plays an important role in the formation of low-temperature sludge in engine oil. It is further known that NO_x reacts with olefin contents of unburned gasoline to form sludge precursors. It is acknowledged that engine operation during stop-and-go driving accelerates sludge formation. In this study, the authors developed an oil evaluation test which combines the stop-and-go driving elements into a single STOP/GO driving mode and investigated why stop-and-go driving accelerates sludge formation. It was found that in low-temperature engine operation in the stop element of the STOP/GO driving mode, NO_x and unburned gasoline are absorbed into the oil, and in high-temperature operation in the go element of the STOP/GO driving mode, NO_x and unburned gasoline are released from the oil. NO_x comes in contact with unburned gasoline in the combustion chamber during the compression stroke and in the vapor of the crankcase ; it reacts with olefins in the unburned gasoline to form sludge.