Unfortunately many car owners take the service routine of their vehicles for granted. Engine oil is the life blood of an engine therefore if anything goes wrong with the engine oil you can be sure that a major engine issue is on it's way.
It is important you understand the kind of oil recommended for your engine and also the recommended interval between each oil change; because lube carried out without the recommended oil grades will be less effective and will ultimately cost more.
When this seemingly simple but extremely important routine is ignored it will lead to build up of sludge which will drastically reduce the lubricating power of the oil in the engine leading to poor supply within the engine which will manifest outwardly in form of: 1. High feel mileage 2. Knocking sound and rough idle