Engine
wear is mainly caused by below-normal running temperature
and ncorrect, or infrequent, servicing. When you start
the engine for the first time in the morning the water,
as well as the engine components, are at the temperature
of their surroundings.
This
means that the oil is thicker than normal and that
the clearances in the engine are larger than their
designed values. This increases the chance of metal-to-metal
contact and also means that some of the water, which
is a product of combustion, gets a chance to mix with
the oil. The conditions are so unfavourable that
it has been calculated that on a trip
from Cape Town to Johannesburg, more than 90 per cent
of the wear takes place during the first 10
minutes of the journey.
What
can one do? Allow the engine to idle until it is at
the working temperature? No, the modern engine responds
best by being driven away immediately at a slower
than normal pace until the water and oil are at their
normal temperatures. This has the further advantage
that the choke is used sparingly, decreasing the chance
of raw fuel getting into the engine, as well as making
sure that the gearbox and final drive also get a chance
to warm up gently.
On
the servicing side, regular changes of filters (air,
oil and fuel) will prevent wear caused by dirt getting
into the engine. However, it is very important to
buy only reputable makes of filters, because South
Africa has been inundated with third-rate automotive
components, and some of these filters are so bad that
they can develop a blockage and cause engine failure.
Driving
habits can also affect engine wear. Habits such as
applying full throttle on a cold engine, regularly
revving into the red zone, and letting the engine
idle for long periods are all harmful. On the other
hand, cruising at any chosen speed in the highest
gear does very little harm to the engine, because
modern gear ratios will normally ensure that the engine
cannot over-rev in top gear.
This
graph shows that a filter's efficiency improves the
longer it filters. It's important to change the cartridge
at the correct (ie recommended) time and not too soon
or too late.
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