Engine oil is the 'life blood' of your car. It's a vital component of the engine system, lubricating moving parts and ensuring your car has a long and happy life. The grade and type of oil you use can also impact your car's economy and emissions, so it is essential that you use the correct grade of oil. Unlike blood, engine oils don't self-cleanse and after a short amount of time will start to degrade and become progressively dirtier and less efficient.
Experts recommend that you should change your engine oil after 3000 miles. It's likely too that you will need to top it up before then, though.