单项选择题
A.valve guides B.oil control rings C.valve seats D.compression rings
For optimum results, centrifugal purification of heavy ...
单项选择题For optimum results, centrifugal purification of heavy fuel oil should be accomplished with the fuel at the lowest practicable（）
A.throughput B.additive percent C.cetane number D.TBN number
Diesel engine piston ring blow-by is usually caused by ...
单项选择题Diesel engine piston ring blow-by is usually caused by excessive ring clearance at the ring（）
A.back B.side C.gap D.bottom
In a four-cycle diesel engine piston blow-by can result...
单项选择题In a four-cycle diesel engine piston blow-by can result in increased（）
A.crankcase pressure B.compression pressure C.scavenge pressure D.exhaust manifold pressure
