Influences of lubricant composition and lead content in gasoline on intake valve deposit.

Abstract

Lubricant composition and lead in gasoline were chosen as two major factors for the formation of intake valve deposit during operation. Several engine tests and a new laboratory test were employed to evaluate the effects of these two factors on the composition as well as the amount of deposits formed.The modified Panel-Coking test, which was developed in the present work, was found to be very suitable for studying intake valve deposit, and the results obtained from this method correlated well with those from engine tests.Although both lubricant composition and lead content of a fuel contribute a great deal to the formation of deposits as reported by several workers, the amount of deposits on the intake valve was found to be dependent primarily on lubricant composition, especially on the concentration of the V. I. improver used and far less on the lead content of the fuel. Also the modified Panel-Coking test suggested some critical temperature-ranges for accumulation of intake valve deposits; for example, 280-330°C for 10W-50, 320-370°C for 10W-30, 350°C<for SAE30 oil.