Regular Car Oil Change
Having clean oil in your can reduce the wear which is caused by friction of the different moving engine parts and also helps to improve your fuel consumption. For this reason it is recommended that you have the oil in your car regularly changed.
If possible keep track of when you last changed oil. Ideally on a petrol car you should change the oil once every year or every 7500 miles, so taking note of your last oil change means you know when you will do need to do another oil change. For a diesel engine it is recommended you change the oil every 6 months or 3000 miles.
Problems
If you don't know how to change the oil in your car ask your garage to do it when you go for a service. It will cost you whether you do it yourself or get a garage do it, however it will help keep your cars engine in good condition which will make it more enjoyable to drive and easier to sell in the future.
Image source: Some rights reserved by Robert Couse-Baker