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  • Cover for when your manufacturer warranty expires
  • Financial protection for used cars from expensive repair costs
  • Car hire, roadside assistance and travel costs covered as standard

What car modifications void your warranty?

If you’re thinking of making changes to your car, you may be wondering what modifications void your car warranty. It is something of a myth that any modifications to a car will void your manufacturer's warranty, or an extended warranty provided by a dealer or warranty specialist. The reality is that you will only face a full or partial void if the need for repairs can be directly linked back to a post manufacture modification, often termed as an 'aftermarket add-on'.

An example might be an engine problem caused by a poorly fitted exhaust upgrade, or an unsanctioned engine rebore resulting in unexpected damage.

Modifications made with approved parts and carried out by an approved engineer will not void your warranty, although it's important that you contact your warranty provider to find out for sure what car modifications void your warranty.

Staying within the law

There are legal restrictions on how you can modify your car and, obviously, anything you do to your vehicle which is illegal will inevitably risk voiding your warranty, even if the reason for repair doesn't appear to be linked. For example:

  • Some under-car neons break the law if they are too bright or render the car a hazard for other drivers.
  • Overly dark window tints on front windows and the windscreen are prohibited. Bear in mind that the light transmission should be a minimum of 70% through the front windows and 75% through the windscreen.
  • Large bore and sports exhaust systems can fall foul of both fuel emission rules and laws limiting noise pollution.

Modifications usually allowed

The following modifications are usually permitted and should not void your warranty, but only when you use approved parts and certified fitting:

  • enlarged brake discs
  • cryo treating the engine
  • most fuel upgrades
  • reboring your engine to increase capacity, raising the RPM and generating more power is permitted but only within specified limits
  • some neon lights are permitted but only if they are not too bright, the tubing is not visible and there is an easily accessible on/off switch
  • adding larger rims or alloy wheels
  • exhaust upgrade with silencer
  • number plate change, as long as you stay within current legislation regarding format, spacing, font and size
  • spoilers, as long as they are of legal size and appropriately fitted
  • tinted windows that fall within the legal limits for opacity

What if I bought the car with the modifications already in place?

If this is the case, then as long as all the modifications are specified at the time of taking out the warranty, you are fully covered and your warranty can't be voided. If you plan to purchase a used car that has been modified and you want to take out a warranty, make sure that all details of the modifications are included in your documentation, either with your dealer or your directly with your warranty provider.

I want to make a modification, but I'm worried about my warranty

If you are planning any modifications to your car, you are strongly advised to check with your warranty provider before you go ahead. Get clear advice about which parts are authorised, and which engineers are certified to carry out the work. It's always best to check first to avoid problems further down the line should you need to make a claim.

Always consult your provider

The overall message regarding modifications is that the most important thing is to check with your warranty provider. By seeking authorisation and clearance prior to making any changes to your vehicle, you will know exactly what - if any - impact they will have on your cover.

Other related FAQs

Looking for more related content to this? We’ve picked a selection of related topics that you may find helpful

Yes, you can usually extend your car warranty cover when it runs out.

Yes, you can cancel your warranty at any point in the first 30 days and be guaranteed a full refund of the cost, providing you haven't already made a claim within this period.

In most cases, car warranty is transferable from one vehicle to another.

There are a number of things that could make your car warranty void, such as modifications, neglect and the use of unapproved fluids.