单项选择题
A.decreased piston to cylinder head clearance
B.increased exhaust system back pressure
C.early fuel injection timing
D.low scavenge air temperature
单项选择题 Whether using a centrifuge or a simple filter, oil cleaning and filtration will be the most effective when the oil is at a （）.
单项选择题 Exhaust valve grooving and corrosion is caused by certain components of residual fuel oilThese components are sodium, sulfur, and （）.
单项选择题 Which of the following problems may occur if the opening pressure of a fuel injection nozzle is greater than specified by the engine manufacturer?（）