单项选择题 In some diesel engine designs,（）the injection of cylinder oil is timed to impinge when the piston and only impinge on（）

单项选择题 （）diesel engines generally have two systems of lubrication:（）a total loss system feeding and a circulating system lubricating the running gear and cooling the pistons.

单项选择题 The following options are all the functions of lubricating oil except（）