题目内容
We cannot eliminate internal friction, but we can reduce it to a controllable degree by the use of ______.
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By______ , reduce friction between moving parts of engine.
By______ , prevent leakage between parts such as pistons, rings and cylinders.
______ can carry away heat by flowing between friction-generating parts.
The oil pump, oil filter and oil pan, make up the _____of the engine.
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