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Technology: Engineering Our World
Oil separates two surfaces that would otherwise touch, rub, and wear
each other away. See Figure 8-64. For good lubrication, oil must have the
right viscosity (thickness). Viscosity is a kind of friction in liquids. It is
caused by the molecules of a liquid rubbing together. Water has a low
viscosity and pours easily. Honey and molasses have a high viscosity, so
they ooze out of containers. Heating honey and some oils will cause them
to flow more easily.
Motor oil becomes thinner (less viscous) as its temperature increases.
In the warm summer months, a thicker oil is needed. However, in the
icy cold of a winter’s morning, a thinner oil is needed for easier starting.
Therefore, multi-grade oils have been developed to meet the needs of
automobile engines in a range of temperatures.
gure 8-64. Oil lubricates parts
to reduce friction.
Think Green
Green Lubrication
Lubricants such as the motor oil used in vehicles are necessary, but
they are not environmentally friendly. Motor oil is not biodegradable, and in
some states, it is considered a hazardous waste. Automobile technicians
are required to recycle used oil and to document the process. Individuals
who change the oil in their vehicles should take the used oil to collection
sites for recycling.
New alternatives to traditional motor oil are becoming available,
however. Argonne National Laboratory has used nanotechnology to
improve traditional motor oils. They combine extremely small particles of
boric acid with motor oils. Each particle of boric acid is only 50 nanometers
in diameter—less than one-thousandth the width of a human hair.
The resulting product is biodegradable, is not a health or environmental
hazard, and does a better job of reducing friction than traditional motor oil.
Engines that have less friction to overcome are more efficient and use less
gasoline. Also, lowering friction can extend the life of the lubricated parts.
Finally, these lubricants only have to be changed every 100,000 miles, so
the vehicle owner spends less time and money changing the oil.