The oil filler cap is a small cap usually made of plastic which is placed on the oil inlet as  a protective covering.

The Oil Filler Cap can be found beneath the bonnet, usually located on top of the engine block, directly on the oil inlet. The cap will usually have a picture of an oil can on it and be in clear view. The oil filler cap normally has a diameter of between 2-5 inches  and is circular in shape.

The oil filler cap prevents dust, dirt and other unwanted debris from entering the oil supply. Dirty engine oil is not good for the car engine and will affect the performance of the engine as well as potentially causing damage to other vital engine components. 

If the oil filler cap is lost or broken it will need replacing as soon as possible. Oil could potentially leak out if the cap is missing or broken and dirt etc. could get into the oil supply. The oil filler cap is the perfect replacement part, specifically designed for the make and model of your vehicle, it will be perfectly compatible.