The Top Reasons Why Your Car May Fail Its MOT This Winter

Taking a vehicle into a dealership or car garage can be a daunting experience for many drivers, not least when it comes to your annual MOT. While some cars will pass without any issues, for others it’s a different story with MOT fails resulting in drivers forking out hundreds of pounds in repair costs.

The winter can be a particularly challenging time for drivers with plummeting temperatures and treacherous road conditions making car maintenance all the more difficult. To help Brits look after their vehicles during the worst of the weather conditions, we’ve taken a deep dive into Department for Transport data. By doing this we’ve been able to unearth the most common reasons cars fail winter MOTs and the locations where MOT failures are most likely to happen. 

Our in-depth analysis of more than 20.2 million car MOT tests across winter 2020 and winter 2021, has revealed:

• On average there are 2 million failed MOT tests each winter
• 1 in 5 (20%) vehicles fail their MOT during the winter months
• Tread depth is the most common reason cars fail their MOT 
• Cars are most likely to fail their MOT in Kirkcaldy, Dundee & Truro and least likely to fail their MOT in Enfield, East London & South East London in the winter

While failures can be caused by countless factors, the good news is there are preventative measures people can take to reduce the risk of their car failing its MOT.

The eye-watering costs of failed MOTs

Having crunched the numbers we found there were a total of 20.2 million winter MOT tests across 2020 and 2021, with 1 in 5 (20%) vehicles failing their annual car safety test. With the cost of living crisis and the aftermath of Christmas, the last thing anyone needs during the winter months is yet another cost. However, our analysis reveals that with an average of 2 million failed MOTs each winter, and the most recent research putting the average cost of a failed test at £326.85, Brits will fork out a staggering £653.7 million for failed tests this winter.

The most common reasons to fail an MOT in the winter 

To help shine a light on the areas of a car that drivers should prioritise looking after, our research has revealed the leading reasons cars fail their MOTs in the winter months. While it’s important to remember a vehicle can fail an MOT for multiple reasons, it’s clear that tyres, brakes and a car’s suspension should be carefully looked after if you want to avoid issues in your next test.

The 20 most common reasons cars fail an MOT in the winter:

Tread depth

The most common reason cars fail an MOT is because of a lack of tread depth – accounting for 36.47% of failures. Good tyre depth is essential for maintaining grip and allowing your car to brake successfully. A lack of tyre depth can heighten your chances of having an accident, especially in the wintertime when icy or wet roads already make braking more difficult. 

The minimum legal requirement for tread depth in the UK is 1.6 millimetres, although we advise you to replace your tyres well before, at 3 millimetres; any less and your stopping distance when braking will start to increase. Testing your car’s tread depth is imperative not least if you’ve bought a used car. To do this, take a 20p coin and run it along the tread groove. If the outer band of the coin disappears you’re good to go, but if you can still see the outer band, it’s time to replace your tyres. 

On top of keeping an eye on tread depth, you must also ensure your tyres are correctly inflated and that you limit heavy braking, acceleration and sharp steering.

Tyre faults

Several different issues fell under tyre faults, the second highest reason for MOT failures. Among them were seriously damaged tyres, visible or damaged tyre cords, a tyre not being fitted correctly and a tyre fouling another part of the vehicle. 

Taking care of your tyres is pretty straightforward though. It is recommended that you change them every 20,000 miles or every 10 years (whichever comes first), and you should regularly check them for visible damage. Look out for cracks or cords which are a telltale sign you need to replace your tyre. 

Brake discs and pads

Appearing at third and fourth were brake discs and pads. These essential components are vital to your car’s braking system and having issues with either or both could significantly affect your ability to stop. 

In the winter, colder temperatures and excessive braking can overwhelm your braking system. To help reduce the risk of issues with your discs and pads we suggest keeping your car in a sheltered area, such as a garage if you have one. Try not to ‘ride on the brakes’ i.e. keeping your foot on the brake for long periods of time. Instead, select a higher gear to control speed and utilise your hand brake and engine braking when coming to a stop.

Coil springs

Part of your vehicle’s suspension, coil springs absorb the impact from potholes, bumps and rough terrain. The cold weather in winter can affect the steel in the springs making them brittle and more likely to break when impacted by harder, tougher and gritted roads. It’s therefore unsurprising to see them contribute to more than 1 in 7 (16.4%) cars failing their MOT across the winter months. 

To help minimise damage to your coil springs, try to avoid potholes where possible and ensure you wash under your car to remove salt from gritted roads which can erode the springs.

The locations where cars are most, and least, likely to fail its winter MOT

Our analysis has also revealed the 20 places where cars are most, and least, likely to fail their winter MOT. Overall, Scotland and the Southwest topped the locations across the UK where you are most likely to fail your MOT in the winter. The postcode KY, which covers the Kirkcaldy area on the east coast of Scotland, was ranked first as the location where you are most likely to fail your MOT. MOT tests taken within the KY postcode had a 27.75% failure rate with 32,853 failures over winter 2020 and 2021. 

The postcode DD, which covers Dundee and is also on the east coast of Scotland, follows in second place with an MOT failure rate of 26.85%. Out of 86,606 tests, there were 23,254 failures. The third area where you are most likely to fail your MOT is within the TR postcode, which covers Truro in Cornwall. Here there’s a failure rate of 25.96% from 133,345 tests.

The 20 locations where cars are most likely to fail an MOT in the winter

Meanwhile, the five postcodes where you are least likely to fail an MOT all sit within London. In a highly trafficked area with extensive public transportation and milder weather conditions, it’s fair to assume the majority of drivers in the capital are less likely to use their vehicles.

The 20 locations where cars are least likely to fail an MOT in the winter

The postcode EN, which covers Enfield, has the lowest failure rate of all locations across the UK at 12.87%. Out of 115,317 tests in winter 2020 and winter 2021, there were a lowly 14,847 failures. MOT tests taken in the postcode E, which covers East London, have the second lowest failure rate of 13.32%, a total of 21,706 failures out of 162,969 tests. It’s also good news for residents who live in the postcode area RM which covers Romford as MOT failure rates are just 14.29%. 

Our top tips for winter car maintenance

As mentioned previously, the winter can create and exacerbate existing issues with your car, escalating problems from relatively easy-to-solve minor inconveniences to expensive repairs and a failed MOT. To help you keep your car on the road throughout the winter, we have compiled a winter car maintenance checklist to ensure your vehicle stays in top condition.

1. Don’t overlook your lights 

As the winter nights roll in it’s vital that you are regularly checking your exterior lights. Number plate lights and headlights need to be working properly, not only for the safety of you and other drivers but also for you to pass your MOT and comply with legal requirements.

To avoid getting into difficulties make sure you check and clean your lights regularly – dirty and salted roads can cause build-up that reduces the brightness of your lights. It is also worth carrying spare bulbs with you. With darker mornings and evenings your lights will be getting more usage which may cause them to blow quicker.

2. Check your exhaust

The freezing temperatures of winter can cause the metal in your exhaust system to contract creating cracks, holes, and other damage exacerbated by salted roads that can cause corrosion.

Avoid damage by checking your exhaust regularly to spot and address any wear and tear early on. If possible, park your vehicle indoors overnight to protect it against nighttime temperature drops. We’d also recommend washing your exhaust system regularly, particularly after driving through gritted and snowy roads, to remove any lingering debris. 

Cleaning your exhaust is a simple yet often overlooked task. To begin, use soap (with a mild polish abrasive), water, and a cloth to clean the exhaust tip. Then, taking a hard bristle brush, scrub the inside of the tailpipe as far down as you can. 

3. Keep on top of your antifreeze

Antifreeze is essential to maintaining the good health of your engine and, despite its name, should be used all year round to prevent water in the engine cooling system from getting too hot or cold. 

In the winter, it is vital that you check your antifreeze and keep it topped up to protect your engine from freezing over and to protect it from corrosion and scale build-up.

4. Look out for oil leaks

Cold weather can put added pressure on your car’s components, with excessive acceleration affecting your gasket which can result in engine oil leaks.

If you notice a brown or black puddle under your car it could be a sign of a leak coming from the engine. More often than not it’s likely to be a small leak – such as one from a valve cover gasket that has come loose and simply needs tightening. If it’s a larger leak, regardless of where you think it’s coming from, it is time to call the garage and get it checked out. An engine leak can cause your engine to fail in as little as half an hour with a replacement costing over £1,500 in most instances.

With the colder weather conditions having an impact on the driving and maintenance of a car it is imperative that drivers take the steps to look after their vehicle as temperatures plummet. 

To improve your chances of passing your MOT follow our expert winter car maintenance tips and check the tread on your tyres, drive in a higher gear if needed and wash underneath your car to remove salt or grit which can erode your suspension.  

If you’re based in Scotland, up north or on the coast remember that weather conditions can be particularly harsh making it all the more important to prioritise taking good care of your car.

Ultimately, regular maintenance of your vehicle and following the owner’s manual is the best way to ensure it runs at full capacity. If you have any concerns about the running of your car you should take it to a specialist and most importantly, don’t just wait for the MOT.

Methodology 

We analysed data from the Department for Transport that provided anonymised MOT test details and results. Looking specifically at the time frame of winter 2020 and 2021 (December 20, January 21, February 21 and December 21, January 22 & February 22) we were able to reveal the most common reasons cars fail a MOT as well as the locations where failures are most likely to happen. 

Calculating the estimated costs of MOT fails this winter: Our analysis revealed there are an average of 2 million MOT fails each winter. With the maximum fee for a car MOT being set by the Government at £54.85 and research by Good Garage Scheme revealing the average cost of repairs for a failed MOT is £272, the total cost of a failed MOT is £326.85, on average. We therefore multiplied the number of MOT fails each winter (2 million) by the average cost of a failed MOT (£326.85) to reveal the estimated costs of MOT fails this winter.