Modified car insurance

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What is modified car insurance?

Whether you’re styling out your motor with tinted windows, investing in new alloy wheels or increasing horsepower, there are an array of different ways to modify a car – but before you splash out on making changes to your car, it’s worth considering how they would affect your car insurance.

Enquiring about modified car insurance could potentially save you money, while there are some modifications which could have the complete opposite effect – so how (and why) do vehicle modifications affect insurance?

Car insurance for vehicles that have been modified is slightly different to ‘traditional’ car insurance as it requires a more specialist approach with knowledge of the specifics of car modifications.

A car modification can be something as minor as adding a spoiler or fitting alloy wheels, all the way up to changing the exhaust to a turbo system. Car modifications can affect the overall value of the vehicle as well as increasing the risk of theft and making it more difficult and expensive to source replacement parts.

As such, modified car insurance can often be more expensive than normal insurance policies – so the need to shop around for the best deal is even more important. Many major car insurers deem modified cars as ‘non-standard’ vehicles, which automatically puts them in a more expensive insurance bracket. However, there are some specialist modified car insurance companies who take a different view and believe that drivers who spend money and time modifying their car are much more likely to take care of it, and set their premiums based on that.

There are many different ways to modify a vehicle; some modifications can be done to improve the performance, whereas others simply make a car look better.

However, although modifications to vehicles may seem like a great idea, you must consider the affect these changes will have on your car insurance premium.

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What is a car modification?

A car modification is a change or addition to a vehicle which will enhance it in some way and is not part of the manufacturer’s original factory specification.

Did you know that something as simple as having a sticker of your favourite football team on your car could invalidate your insurance if not declared to your provider? This is because the sticker could increase the risk of your vehicle being vandalised, and therefore would increase the amount you are required to pay for cover.

A ‘baby on board’ sticker or an air freshener on your rearview mirror (as long as they aren’t obstructing your view) aren’t usually classed as modifications and should not have an impact on the validity of your car insurance. However, adding a roof rack to the top of your motor without informing your insurance provider could land you in a sticky situation.

Modifications which could have a detrimental impact on your insurance premium include:

  • Turbo/supercharging
  • Wheel arches
  • Roll bars/cages
  • New/replacement seats
  • Exhaust changes
  • Tinted windows
  • Car phone kit/stereo/sat nav
  • Decals (stickers, stripes, etc.)
  • Specialised paintwork

Car modifications that don’t affect car insurance

While modified cars are typically more expensive to insure, there are a few changes you can make to a vehicle which won’t have a negative impact on your insurance premiums – in fact, some can help to reduce your cover.

Some modifications which could reduce the cost of your car insurance include:

  • Dash cams – insurers like Admiral offer dash cam car insurance discounts
  • Tow bars – having a tow bar fitted implies that you’ll be driving slower
  • Black box – a telematics (or black box) policy bases the cost on your driving ability
  • Parking sensors – having a parking sensor reduces the likelihood of you making a claim

Why is car insurance affected by modifications?

Car insurance premiums are calculated with consideration of risk and how likely your insurance provider believes you are to make a claim.

Cars which have been modified are statistically more likely to be involved in an accident, while even vehicles with altered paintwork or external decals can be seen as more likely to be targeted by vandals.

Modifications like parking sensors can reduce the cost of insurance, as it is hoped that you would be less likely to claim following some bad reverse parking.

Generally, most of the performance and aesthetic modifications will increase the cost of your car insurance premium. Other changes such as those made to improve safety, eg. parking sensors, won’t affect premiums and could help you avoid accidents which, over time can reduce your premiums.

Below you can see why certain modifications will affect the amount you pay.

  • Risk of accident – Some car modifications improve performance and in turn, increase the risk of having an accident. Because of this, insurers will increase premiums.
  • Risk of theft – Some modifications are high in value, for example, sound systems and satellite navigation systems. Having these valuable modifications in your car will increase the risk of theft, again, increasing your premium.
  • Value of vehicle – Most modifications you make to a vehicle are not cheap to make, and due to this, the overall value of the car will increase. Insurers tend to charge more to insure vehicles which will cost more to replace or repair if they were to be in an accident.

How is car insurance affected by modifications?

Below is a list of common car modifications and the average increase/decrease in premium price due to each modification.

Engine and mechanics

–        Turbo/Supercharging                                      132% increase

–        Transmission/Gear change                             63% increase

–        Exhaust changes                                             26% increase


–        Wheel arches                                                  66% increase

–        Complete body kit                                           57% increase

–        Spoilers                                                           23% increase

–        Light changes                                                  12% increase

–        Tinted windows                                               16% increase


–        Replacement of seats                                     27% increase

–        Replacement of steering wheel                     41% increase

–        Dashboard changes                                        16% increase

Brakes and suspension

–        Uprated brakes                                               36% increase

–        Suspension                                                      25% increase


–        Specialised paintwork                                     36% increase

–        Stripes and badges                                          22% increase


–        Alloy wheels                                                    8% increase

Fuel economy

–        LPG conversion                                               15% increase

Driver aids

–        Satellite navigation system                             15% increase

–        Car phone kit                                                  26% increase

–        Parking sensors                                               13% decrease


What modifications void car insurance?

If you modify your car without informing your insurer, there is always a chance that your insurance could be void.

Whether you’re adding a new spoiler or simply sticking some decal stickers on your bonnet, it is always worth giving your car insurance provider a call to establish whether or not it will impact your cover.

They may request that you pay more (plus a possible admin fee) for the changes made, so if you can, wait until your policy is nearing its end before considering any modifications. That way, you won’t have to pay an administration fee and will have the option to shop around for a cheaper deal.

Modified car insurance for young drivers

Car insurance for young drivers is expensive, even on the most mundane vehicle; on a car which is statistically more likely to be involved in an accident, car insurance could potentially cost you thousands of pounds.

As a young driver, the only modification that we can recommend to keep your insurance premiums to a minimum is having a black box fitted by your insurance provider. Having a telematics car insurance policy can be rewarding if you drive safely and within the speed limit.

If you are a young driver with a modified car then, as always, we would recommend that you shop around to find the best deal – beware, though, that with the combined risk of a new driver and a modified car, you may struggle to find reasonably priced cover.

Notifying your car insurance company of a modification

When searching for car insurance you must always inform your insurers of any modifications made to your vehicle. Even if you purchased the car with these changes. Failure to do so may result in your policy not paying out.

If you already have a policy in place and decide to make changes to your car, you must let your insurance company know as soon as you do so. Do not wait until it is time to renew, as again, your policy could be invalidated.

What modifications are illegal on cars? Illegal car modifications UK

While modifying your car can make it seem more original and personal to you, some vehicle modifications are illegal.

UK car modification laws are quite strict, but are not common knowledge to many. They also need to be read carefully to ensure that you fully understand what they mean.

For example, fitting neon lights to your car is legal in some cases but not others – you can’t add any green lights, flashing/spinning lights to a vehicle, and any lights that are fitted aren’t allowed to be visible from within the car; this would be classed as a distraction.

Similar laws apply to window tinting in the way that it is legal, but only to a certain extent. If your windows are tinted too much then the police will know and have specialist equipment to prove your guilt – if you’re caught, you’ll be told not to drive the car until the windows are changed.

Some more serious examples of illegal car modifications include are the removal of the catalytic converter in the exhaust, tuning the car’s on-board ECU to improve vehicle performance and the injection of nitrous oxide into a fuel tank.

Why car modifications may not be the best idea…

As well as the risk of increased car insurance premiums, modifying your car can cause a lot of other detrimental effects. We’ve listed a few of them below just so you’re aware of some of the potential issues you could run into:

Fuel economy

As modified vehicles tend to be heavier – especially those with bigger wheels fitted – this will negatively affect the fuel economy of your car, meaning you’ll be visiting the petrol/diesel pumps a lot more!

Sports exhaust have the same effect. You may get heads turning with that loud exhaust while you cruise about town, but the overall performance of the car will be affected.


Your bigger wheels can also have an impact on how well your car manages on the road – which is a cause for concern when you factor in the notoriously poor state of many roads in the UK.

Many modified wheels are also fitted with low profile tyres, which means they are a lot more likely to suffer punctures.

Noise and emission guidelines

You know that part of your MOT test that deals with the noise and emissions output of your car? Well, modified cars could lead to you failing that part of the test due to producing too much noise and exceeding the emissions levels.

How to tell if a car has been modified

With many modified cars, it is obvious that they have been ‘upgraded’ by the owner (the huge exhausts, shiny rims and massive spoilers can be a giveaway). However, it’s not always that easy to spot – so if you are thinking about buying a second-hand car here’s a few tips to help you spot any modifications:

Ask the owner – an obvious tip, but you may not always get an honest answer

Common car mods to look out for/ask about are:

  • Bigger wheels
  • Alloy wheels
  • Adjusted suspension
  • Sports exhausts
  • Spoilers
  • Tinted windows
  • Upgraded stereo systems

If you suspect that any of the above are not ‘factory-fitted’, and you are not convinced by the current car owners insistence that they are, then refer to the vehicles specifications (which can easily be found online).


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