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Soiled plugs, tired engine

Question : MY Toyota Corolla 1300 is 16 years old and has clocked 140,000km.

Over the past five years, the car is mainly driven just from my home to the LRT station and back, a total of approximately 2km. I service the car at intervals of six months since it hardly travels 2,000km in this time.

At my last service, I have noticed that my spark plugs were covered with oil and soot. Please advise as to what the causes might be, and whether the low mileage and utilisation will affect the engine in the long run.

Answer : MODERN engines have longer service lives compared with the engines manufactured in the 1960s and 1970s. The reasons are better manufacturing technology and materials, and also a marked improvement in the quality of lubricants.

However, the actual life of the engine in service depends on numerous factors, such as regularity of service, the type of lubricant used, the ambient temperatures under which the engine is operated and the type of usage the engine has been put through.

The presence of oil and soot on the spark plugs does not normally bode well for your engine. In most cases, it is a sign of extensive engine wear.

The presence of engine oil or engine oil deposits on the spark plugs mean that an excessive amount of engine oil is entering the combustion chamber, the oil is not burnt off and is deposited as a heavy layer of soot on the plugs.

This is usually accompanied by an increase in oil consumption. Unfortunately, when a situation like this arises, the only solution is a complete engine overhaul, often at a substantial cost.

A cheaper solution is to fit a used engine, but there are risks since there is no way of telling the condition of an engine that has, been removed from the vehicle, save by examining the spark plugs.

Short journeys will shorten the overall life of your engine because the engine does not get to warm up properly.

Cold running shortens engine life because moisture from combustion condenses and combines with residues to form acids which are corrosive to engine components. Cold running also means more fuel is required, and the excess washes lubricants off the engine walls.

Also, engine components do not reach their optimum operating temperature where they are able to operate smoothly.


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