4 Factors to Consider When Modifying Your Car

Modifying your car is a great way to add personality and individual flair. Some smart mods can also improve handling and performance, and even increase the value of the car if you’re thinking about selling.

There are many different kinds of modifications to suit all types of drivers, vehicles and budgets. From purely aesthetic mods like a custom paint job to high-performance modifications like engine upgrades and turbos, there’s a heap you can do to make your vehicle stand out from the crowd.

Broadly speaking, there are three types of mods: performance, functional and aesthetic.

Performance mods are designed to alter the performance of the vehicle including the speed, acceleration, handling and fuel efficiency. These can include modifications made to the engine, exhaust system, cooling system, brakes, suspension, and tyres. Read some of the common engine problems and their causes. When it comes to performance mods, it’s worth remembering that an upgrade to one aspect of the vehicle can lead to a decline in other areas. For example, a power upgrade can result in a decline in handling and road holding.

Functional modifications add or alter functional components of a vehicle. These can include the addition of sunroofs, air conditioning, communication or stereo systems, roof racks, navigation system or additional storage. These shouldn’t affect the performance or handling of the vehicle, although in some cases major functional modifications can add significant weight to a vehicle, affect the balance or aerodynamics and even affect the electrical system.

Aesthetic modifications primarily affect the look of the vehicle. These mods can include custom paintwork, body kits, window tinting, and cosmetic lighting. In some cases, aesthetic modifications may also be designed to affect performance and handling, such as body kits designed to improve aerodynamics.

Whatever modifications you are considering, it’s worth thinking about the effects they may have beyond the mods themselves. Different mods will have different impacts on the vehicle, not all of which you might be prepared for.

So before you commit to any modifications, it’s worth considering a number of potential issues that may arise.


Before you start adding body kits or superchargers to your vehicle, you should be aware that modifications can seriously affect insurance costs and coverage.

Car insurance is broadly calculated based on three factors: the likelihood of the vehicle being stolen, the risk of accident, and repair and replacement costs. So from the point of view of an insurer, a modification could increase one or all of these factors.

Car Mechanic Point Cook

While most good insurers include common modifications in their policies, it’s important to check with your insurer before making any modifications to your vehicle. While minor functional or aesthetic modifications, like adding a roof rack or body kit, are unlikely to significantly affect your premiums (if at all), performance modifications could have a major effect on the cost of your insurance.

Most insurers have a list of modifications that aren’t included in their coverage. These can include mods like:

  • Custom paint or specialised paint (after market)
  • Nitro or hydrogen fuel modifications
  • Aftermarket petrol turbo or supercharger
  • Roll bar/roll cage/racing harness

Adding some of these mods without consulting your insurer could even void your policy, meaning you may no longer be covered in case of an accident.

Roadworthiness (and legality)

There are a number of modifications that can affect the roadworthiness of your vehicle, potentially making it illegal to drive on Australia roads.

According to VicRoads, “Modifications to vehicles have the potential to adversely affect its compliance with the Standards for Registration by altering its structural integrity, the operation of safety systems, handling characteristics or emissions compliance.”

In Victoria, VicRoads clearly lays out the rules for light vehicle modifications. In particular, this includes information about common modifications like window tinting; adding, removing and replacing seats; adding or removing fog lights or headlights; and modifications to bullbars.

Before making modifications to your vehicle it’s recommended that you discuss your plans with a VASS Signatory, who will be able to provide you with advice and guidance about what will be required in the process of obtaining a VASS Approval Certificate. This will give you a higher chance of ensuring your vehicle will meet the Standards for Registration when your modifications are complete.


If you follow the VicRoads guidelines and have all modifications professionally carried out and inspected by a qualified mechanic, then mods should be safe. However, it’s important to be aware how your modifications could affect the safety of your vehicle.

Any changes to your vehicle’s stock factory setup could result in changes to performance and handling or compromise the safety systems. Installing improper or poor quality parts can affect the safe operation of the vehicle, especially when dealing with vital systems like brakes, suspension and wheels and tyres.

Even something as simple as adding custom seat covers could interfere with seat-mounted side-impact airbags.

Consider how safety systems or vehicle handling may be affected by your modifications and always check with your mechanic before making changes to vital systems.


While adding modifications doesn’t automatically void a vehicle’s warranty, it can affect your warranty’s coverage. In many cases, a modification will only affect the warranty if the manufacturer or dealer can prove that the modification played a part in the need for repairs. For example, your warranty may still be valid if your radiator springs a leak, despite adding an aftermarket exhaust, since the exhaust system didn’t play a part in causing the radiator leak.

However, it’s important to note that it’s often not entirely clear what components played a part in a vehicle problem. In some cases, it may be enough for the manufacturer/dealer to simply say the modification may have contributed to the problem. And that could be enough to void the warranty. Therefore, it’s always worth carefully reading the warranty fine print before making any vehicle modifications, just in case.

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