单项选择题
A.reduce the wear of bearing surfaces
B.cool the bearing surfaces
C.assist in sealing bearing surfaces
D.all of the above
单项选择题 Which of the terms listed below represents the operational speed at which excessive engine vibration is created?（）
单项选择题 A dirty fuel oil filter is can be detected by （） Ⅰ.fuel oil analysis Ⅱ.observing the pressure drop across the filter
单项选择题 The function of the after-cooler installed between the turbocharger and intake manifold on some diesel engine, is to （）