Every vehicle owner knows that replacing the engine oil at periodic intervals is crucial in keeping the optimum working condition of the engine. However, did you know that there is a right and wrong way of changing car oil?

There are definitely right and wrong ways to change the oil in an engine. Assuming the new oil is of a good quality and a suitable grade, filled to the correct level, the most likely mistake will be how the old oil is drained out.

Oil should be drained as soon as possible after the engine has been running at normal temperature, so the oil is hot and runny and all the “dirt” in it is still churned up. Also, the filler cap must be removed before the drain plug is loosened. And the vehicle should be on a flat surface.

 All of that is necessary to ensure the oil flows out with maximum speed, carrying all the dirt with it and leaving as little as possible of the old oil clinging to the walls and components of the engine, to minimise residual sediments.

Doing this when the car is flat is important because the sump is shaped to ensure everything drains out when it is horizontal. If the car is tilted, the drain plug hole will be above parts of the sump and ponds of old oil will be left behind.

 The black colour of old oil is mostly soot generated by combustion in the engine, which accumulates over time. In new petrol engines, the quantities are minute, and even though there are millions of combustion strokes between oil changes, the oil can remain clear and golden. As the engine wears, contact with the soot in the combustion chamber and elsewhere increases, the level of soot in combustion increases, residual dirt accumulates, and the oil can become black well before an oil change is due.

 This source of soot is microscopically fine and not hard, and, therefore, not significantly abrasive. So, the oil can still do its lubricating job adequately (though not perfectly) until the due time for change, as long as there is not too much other detritus (shavings of metal from engine wear or dust particles from the air ingested for combustion) suspended in it.

 If the oil gets so dirty with soot and other substances (more prevalent in diesel engines) that it becomes less thin and slippery and more thick and sludgy, it should be changed without delay, irrespective of the scheduled service interval. It is the consistency and smoothness more than the colour of the oil that matters. If you take a sample of oil from the dipstick and rub it between your thumb and forefinger, and there is any sense of grit or stickiness, change it.

 If the oil is not drained properly when being changed, some “sooty” oil will be left behind to mix with the new almost immediately. That is why the correct draining process is important.

Another common malpractice in oil changes is the way the oil drain plug is removed and refitted. It has a sunken head (a protruding nut would risk contact with the road surface or damage from flying stones) which requires a specialised spanner (Allen Key, also known as a hex key or a larger hex wrench) of exactly the right size.

Many garages do not have a comprehensive range of those, and resort to using a chisel and mallet instead. This can distort the plug so no hex key will ever fit in it again, and in extreme cases (for instance when “hammer-and-chisel” open for the 20th time) become misshapen enough that it allows oil to leak out.

 Ideally, the plug should be refitted using a torque spanner set to the design tightness. Too loose and the seal may not be sound and allow leakage and the plug could work loose and literally fall out during ongoing use.

Too tight, and the plug could distort its own threads, with similar consequences, or require even more (damaging) vigour with a hammer and chisel the next time it has to be removed for an oil change.

 The drain plug threads should be kept clean (not tossed on a gritty workshop floor) and the integrity of the washer should be checked. The quality of the new oil filter is also important, as is its pre-fit lubrication and straight attachmen to the correct tightness.

Most vehicle owners ask how many quarts of oil change they have to prepare for. This depends on the size of the engine mounted on their cars. For obvious reasons, the bigger the engine, the more oil it will need.

Engine oil lubricates the different components of the engine. Adequate lubrication prevents friction between the metal components. This helps prevent the buildup of heat. Some modern car engines come with additional cooling measures.

They help the motor oil in keeping the engine from overheating.

In addition to lubrication, motor oil also has cleaning properties. It removes deposits that may have accumulated in critical engine parts. It also removes other contaminants that may affect the performance of the engine.

Given the critical function of motor oil, it is important to put only the correct amount. Remember the bigger the engine, the more motor oil it needs. Bigger engines have bigger components that require adequate lubrication.

In general, cars with four-cylinder engines have an oil capacity of five quarts. Vehicles with six-cylinder engines will often use about six quarts. And if you happen to own an eight-cylinder powerhouse, then you can expect to use about eight quarts of oil.

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