Oil is essential for your engine, because it lets metal press against metal without damage. For example, it lubricates the pistons as they move up and down in the cylinders. Without oil, the metal-on-metal friction generates so much heat that eventually the surfaces weld themselves together, and the engine seizes.
Let’s say that your engine has plenty of oil, but you never change it. Two things will definitely happen :
Dirt will accumulate in the oil. The filter will remove the dirt for a while, but after some time, the filter will clog and the dirty oil will automatically bypass the filter through a relief valve. Dirty oil is thick and abrasive, so it causes more wear.
Additives in the oil like detergents, dispersants, rust-fighters and friction-reducers will wear out, so the oil won’t lubricate as well as it should do.
Eventually, as the oil gets dirtier and dirtier, it will stop lubricating and the engine will quickly wear and fail. Therefore, it is imperative to change oil periodically.
An oil and filter change involves draining out the old motor oil, and replacing it with fresh, new motor oil besides changing the filter.
There is no clear-cut answer about exact interval at which the oil needs to be changed. This is because there are many factors at work : the condition & age of engine, the type of oil used, how you drive, the external environment you drive in, and stop-&-go versus highway driving etc. Owner’s manual recommendations for oil and filter change vary from 5,000 kms to 15,000 kms.
As a general thumb-rule, it is advisable to ask your mechanic, while changing oil, about the next change. Don’t worry – in most good service-centers, they would affix a small sticker giving the next change due. Just follow that and you’ll be okay.
Oil serves many crucial functions, and clean oil performs those functions better than dirty oil. In fact, oil is relatively inexpensive, and changing your oil regularly is a cheap insurance policy against major repairs down the road.
There are many different brands of lubricants available in the market and each has different performance characteristics. The cheaper lubes available in the market use inferior quality of base oil along with poor-quality additives, all of which result in less-than-optimal performance. Oil is very critical for your car – therefore, it is advisable to use oil of a reputed and trusted brand only.