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Motor vehicles that consistently experience traffic like this have increased wear and tear on engine parts, thus requiring more frequent oil changes.

Paul Messam, Gleaner Writer

LET THE engine idle and watch the exhaust pipe. If you spot blue smoke, look elsewhere, because the engine is burning oil.

Are oil changes really that important?

"Yes, because oil in the motor vehicle eventually wears out and its additives get used up," advises Kurt Harding, a St Andrew-based auto mechanic for more than 25 years. "Oil provides the final seal between pistons, piston rings and cylinder walls, ensuring good compression."

Multiple roles of oil

According to him, motorists unfortunately overlook the multiple roles performed by engine oil. "In addition to providing lubrication or actually separating all the moving parts with a thin slippery film, the oil must clean, protect against rust corrosion and assist in cooling the engine," adds Harding.

He points out that motorists should not just take the car in for an oil change because the manual recommends it after a certain number of miles, as the change interval recommended by the manufacturer only applies when the car is operated under favourable conditions.

However, most cars may not necessarily be operating under favourable conditions. If all cars were highway-driven at maximum speed limits, with little stop-and-go city driving, a 4,000-mile oil change, for example, would be enough. On the other hand, a driver who makes only short city runs in cold weather could ruin the engine by waiting up to, say, 4,000 miles before changing the oil.

"In other words, the way you drive and the climate make a difference," says Harding. "Service is recommended at a certain mileage or time, whichever comes first." According to him, if the motorist does not run up a lot of miles, the car should be serviced by the time interval. He notes that severe servicing is required for cars that make frequent short trips to the mall, post office, bank or to work around the capital city. Such vehicles, Harding argues, will need more frequent changes of oil and transmission fluid.

It must be remembered that the camshaft and other parts can be damaged when the anti-wear additive is all gone. Harding warns that sludge and deposits can build up fast after the detergents have been used up. When the antioxidant is gone, the oil can become too thick. Condensation and combustion produce water and acids, and corrosive acid action can be as damaging to the engine as frictional wear.

For each gallon of fuel burned during combustion, nearly one gallon of water is produced. Most of this water is expelled through the exhaust, but some find its way into the oil. Water is heavier than oil, therefore, should the two be mixed, the oil will rise to the top, Harding states.

He says, however, when oil and water are forced under pressure through the engine's moving parts, both liquids soon emulsify and the water is permanently held in suspension. This mixture, together with the products of combustion, forms corrosive acids, gums, varnish, and sludge. The mechanic further explains that if this condition is allowed to continue, the resulting contamination can cause the piston rings to stick in their grooves, and can coat the inside of the oil-fed passages. Thus restricting or completely plugging the flow of lubricant.

Motorists should thoroughly read their manuals regardless of the kind of car they own, and seek advice when necessary. We must remember that oils are unable to do their job when they become heavily contaminated with carbon, water, lead, salts and other products developed in the combustion chamber.