Drivers who plan to soup up their cars should bear in mind that their modifications can lead to a hike in insurance premiums.
Fitting a turbo engine could see the cost of cover rise by more than 130%, according to analysis by Moneysupermarket of more than two million quotes.
And motorists who don’t inform their insurers about any modifications they carry out face having their policies invalidated, leaving them without cover should they need to make a claim.
The research found that fitting a turbo engine sees the average premium rise from £494 to £1,146. Drivers can also see significant spikes to their insurance costs if they change the bodywork by adding a bonnet bulge, flared wings or wheel arches.
Even making simple changes such as having the paintwork redone or adding go-faster stripes can result in a rise in premiums of up to a third.
“Modifications can be a great way to personalise a car, and in some instances will improve performance, but they can quickly bump up the cost of your car insurance,” said Kevin Pratt, of Moneysupermarket.
“Insurance is based on risk, and modifying your car is a warning sign to insurers.
“For example, spoilers or turbo engines will mean a vehicle goes faster, and therefore increase the likelihood of an accident, while car phones and sat-navs are attractive to opportunistic thieves, so insurers balance the scales by pushing premiums up.
“For some, modifications are an addictive hobby, but the most important thing to remember is to inform your insurer of any changes, preferably before you make them, so you can find out the impact on your insurance. You certainly shouldn’t wait until it’s time to renew your policy.”
Other changes that can lead to a rise in premiums include changes to the brakes, the exhaust or the suspension.
At the other end of the scale, though, adding parking sensors results in the average quote falling by an average of 13%, and fixing a tow bar (which usually signifies that you’re a slower driver) lead to an average cut of 20%.