But when the politician or the engineer refers to oil, he almost always means mineral oil, the oil that drives tanks, aero planes and warships, motor-cars and diesel locomotives, the oil that is used to lubricate all kinds of machinery.

但是，政客或工程师谈到油的时候，他所指的几乎总是矿物油。这种油可以用来开坦克，开飞机，开军舰，开汽车，开柴油机

车，可以用来润滑各种机械。

This is the oil that has changed the life of the common man.

就是这种油改变了普通人的生活。

When it is refined into petrol it is used to drive the internal combustion engine.

这种油经过提炼变成汽油以后，可以用来开动内燃机。

To it we owe the existence of the motor-car, which has replaced the private carriage drawn by the horse.

就是因为有了这种油，我们才能用上汽车，以代替马车。

To it we owe the possibility of flying.

就是因为有了这种油，我们才有可能飞行。

It has changed the methods of warfare on land and sea.

它还改变了陆战和海战的方法。

This kind of oil comes out of the earth.

这种油来源于地下。

Because it burns well, it is used as fuel and in some ways it is superior to coal in this respect.

它因为易于燃烧，可以用作燃料，而且在这方面比煤还有若干优越之处。

Many big ships now burn oil instead of coal.

现在许多大轮船就烧油而不烧煤。

Because it burns brightly, it is used for illumination; countless homes are still illuminated with oil-burning lamps.

它因为燃烧时非常明亮，也可以用来照明，许多家庭现在仍靠油灯照明。

Because it is very slippery, it is used for lubrication.

它因为非常滑润，所以可以用作润滑剂。

Two metal surfaces rubbing together cause friction and heat; but if they are separated by a thin film of oil, the friction and heat are reduced.

两个金属面相擦，就要产生摩擦和热;但如果在它们之间抹上薄薄的一层油，就可以减少摩擦，降低热度。

No machine would work for long if it were not properly lubricated.

任何机械如果不使用一定的润滑剂，就不能持续工作。

The oil used for this purpose must be of the correct thickness; if it is too thin it will not give sufficient lubrication, and if it is too thick it will not reach all parts that must be lubricated.

润滑油的浓度必须适当，太稀则起不到应有的润滑作用，太稠则流不到所有需要润滑的零件。

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