In order for insurance companies to supply the correct level of motor insurance, the companies put cars into classification between 1 and 20. This enables insurers to link car that have similar characteristics.
Within these classifications 1 is the lowest group and 20 is the highest group of car. Your insurance premium will be affected by the grouping that your car falls into.
Your every day car, such as a Ford Fiesta will normally fall into the lower insurance grouping, between 6 and 12 (that's if you don't have the RS turbo version). But sports and high power cars, like the Ford RS turbo will fall into a higher classification as they are seen as high risk.
So when you are looking to buy a car you should consider the insurance grouping of the car, in order to have some idea of the premium you are going to have to pay.
REMEMBER!! The lower the insurance group the less premiums you have to pay.
Here are some examples so you can see how it works:
Lower Group Cars
Middle Group Cars
Higher Group Cars
Dreamland Group Cars