Every year, millions of UK cars trundle into a garage for their MOT. The testers poke, probe and prod. They note every advisory, every failure. And then the Department for Transport publishes all of it as open data.
Nearly 200 million tests. 2020 to 2024. Every make, every model, every failure reason, every mileage band.
This data is rarely processed at model level and translated into plain English. We asked: which cars fail most? What breaks first? At what mileage does everything start going wrong? And how does your specific car compare to every other one like it on UK roads?
We did. Here is what the data says.
Which UK Car Has the Highest MOT Failure Rate?
Let us get the big one out of the way first. If you want the car with the highest MOT failure rate among mainstream UK vehicles, the data has a clear answer: the Ford Ka.
At 80,000 to 100,000 miles, over 40% of Ford Kas have issues noted at their MOT. For context, the UK average across all cars is substantially lower. This is not a marginal finding buried in the data. It is one of the clearest signals in the entire dataset.
But that is not the finding that will keep you up at night. This is.
1 in 4 Ford Kas are flagged for structural corrosion around the seatbelt mounts
At 100,000 to 120,000 miles, 24% of Ford Kas are flagged at their MOT for structural corrosion near the seatbelt anchor points. In plain English: the part of the car that your seatbelt bolts to is corroding. This is noted at nearly 30 times the UK average rate for cars of the same age.
This is not a cosmetic rust issue. Seatbelt anchor points are load-bearing. In a collision, the belt absorbs several tonnes of force. If the structure around it is compromised, the belt cannot do its job. The government data is not being dramatic. Neither are we.
The Ford Ka was a beloved car. Cheap to run, easy to park, genuinely cheerful to drive. But the data is unambiguous about what happens at higher mileages. If you are buying one, or you already own one with significant miles, this is the first thing you check.
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At What Mileage Do Cars Start Failing Their MOT?
If there is one number from this analysis that every used car buyer should remember, it is 60,000.
60,000 to 80,000 miles is a critical threshold for used car buyers. It is the mileage band where many major components first start showing wear, and it is also the mileage at which a large proportion of used cars change hands. Accumulated wear on suspension components, bushes, and brake systems starts showing up in force. The seller has hit the first significant maintenance cliff edge and decided that now is a good time to move the car on. You, the buyer, are about to become very familiar with the local garage.
"60,000 to 80,000 miles is when problems start mounting. It is also when most used cars are sold. This is not a coincidence."
This does not mean you should never buy a car with 60,000 to 80,000 miles. It means you should know what you are buying. On some models, 70,000 miles is genuinely uneventful. On others, the defect rate at that mileage is several times the average for all UK cars. The difference is entirely model-specific, and that is exactly the kind of data that no standard history check will ever tell you.
What Are the Most Common MOT Failures in the UK?
Ask most people what causes the most MOT failures and they will say lights, or tyres, or brakes. The data disagrees.
The single biggest category of MOT failures across nearly 200 million tests is suspension. Specifically, suspension component mounting areas and suspension arm pins and bushes account for more total defects than any other category in the dataset.
The most common specific failure, in terms of raw numbers, is corroded brake pipes. Over 10 million instances of this defect appear in the data across the five-year period. Corroded brake pipes are not a niche problem on obscure vehicles. They are the single most documented specific failure on British roads.
| Failure category | Defect annotations in dataset | Risk level |
|---|---|---|
| Suspension component mounting areas | 100+ million | High |
| Suspension arm pins and bushes | 72+ million | High |
| Brake pipe corrosion (specific) | 10.2 million | Safety critical |
| Spring fracture or failure | 6 million | High |
| Suspension component corrosion | 4.4 million | High |
Counts reflect defect annotations across model and mileage groups where the rate exceeded the national average. Figures include advisories and failures.
The point is not that brake pipes and suspension are surprising failures. The point is that your next car has a specific statistical profile for each of these, based on its model, age, and mileage band, and you can look that up before you hand over any money. Most buyers do not know this is possible.
Which Cars Have the Most Unusual MOT Failures?
Some of the most striking findings in the data are not about overall failure rates, but about specific failure types that appear on certain models at rates that are genuinely hard to explain without knowing the car's engineering quirks. A few highlights.
The Land Rover Defender
Corroded brake pipes are noted on over half of Land Rover Defenders at higher mileages
On some Defender variants, corroded brake pipes are noted on over half of all examples tested at 100,000 to 120,000 miles. This is a function of the Defender's legendary ability to go places that corrode brake pipes at an accelerated rate. If you love a Defender, the data loves you back. It just also wants you to budget for brake pipe replacement.
This will not surprise anyone who has owned a Defender. It will, however, be very useful information for the person who is considering buying one without that context. A Defender at 110,000 miles is probably not far from needing new brake pipes. At £300 to £800 depending on who does the work, that is a negotiation point before you buy, not a nasty surprise afterwards.
The Suzuki Jimny
The Jimny is a small off-road vehicle with a devoted following and an almost aggressive cheerfulness about its limitations. The MOT data has noticed the Jimny too.
The Suzuki Jimny is over 1,000 times more likely than a typical UK car to have steering components flagged
At 20,000 to 40,000 miles, the Jimny's stub axle swivel pin defect rate is 1,122 times the UK average for cars of the same age. In absolute terms, around 1 in 300 Jimnys at this mileage are affected, but because this type of failure is virtually unheard of on most modern cars, the ratio is enormous. This is a known engineering characteristic of the Jimny's solid front axle setup. It is not alarming if you know about it. It is very alarming if you do not.
To be clear about what this means: this is not a safety scandal. It is a known characteristic of a specific mechanical design. Jimny owners tend to know about it. People buying their first Jimny sometimes do not. The data is not telling you not to buy one. It is telling you what to expect and what to maintain.
The Renault Scenic
Of all the findings in this dataset, the Renault Scenic's parking brake situation is perhaps the most surprising for a mainstream family car.
The Renault Scenic's electronic parking brake is flagged at 622 times the rate of a typical car
Even at relatively low mileages (0 to 20,000 miles), Renault Scenic electronic parking brake system defects appear in MOT data at 622 times the national average. The Renault Laguna and Grand Scenic show similar patterns. Renault's electronic parking brake system is a known weak point across this model range.
The Scenic is a fine family car. But its parking brake issue is well documented by garages and less well documented by anyone selling you one. Fixing an electronic parking brake actuator on a Renault can cost £300 to £600. That is a meaningful cost on what is typically a budget family buy.
The Citroen C5
We cannot write about MOT anomalies without mentioning the Citroen C5 and its extraordinary relationship with hydraulic suspension fluid.
The C5 uses a hydropneumatic suspension system that is genuinely brilliant when it works and genuinely expensive when it does not. The data reflects this: the C5's hydraulic fluid leak rate is over 1,000 times the national average for fluid-related failures. If you are considering a C5, you either know about the suspension system and have budgeted accordingly, or this is the moment you find out.
Do Electric Cars Fail Their MOT?
Because the question is always asked: what does the data say about electric vehicles?
Electric cars do not have combustion engines, gearboxes, or exhaust systems, so they sidestep a significant proportion of traditional failure categories. But they are not immune. Suspension, brakes, tyres, and lights all still apply. And some specific EV models have their own anomalies.
The Tesla Model S, for example, appears in the data at higher mileages (120,000 to 150,000 miles) with a tyre pressure monitoring system (TPMS) failure rate that is 18 times the UK average. The early Nissan Leaf appears with various suspension-related anomalies. The G-Wiz, if you have one for reasons we respect, has some extraordinary findings that are best left for another article.
EVs are not a free pass on maintenance. They are just a different maintenance profile.
How Can MOT Data Help You Buy a Better Used Car?
The purpose of all of this is not to make you paranoid about used cars. The UK used car market is enormous and the vast majority of transactions are fine. The purpose is to give you the same information that every experienced mechanic already has in their head, translated from the jargon of MOT test sheets into something you can actually use.
A standard car history check will tell you whether your prospective purchase was stolen, written off, or has outstanding finance. It will not tell you:
- That this model has suspension bushes flagged at three times the average rate at 70,000 miles
- That the brake pipes on this specific type are likely to need replacement within the next 12 months
- What those repairs will cost at an independent garage versus a main dealer
- What to physically look for when you go to view the car
That gap between what a history check tells you and what you actually need to know is exactly what we built Carwise to fill. Enter a registration number and you get the full picture: the car's specific MOT history cross-referenced against the model-wide failure patterns, a plain-English summary of what to watch for, known issues with repair costs across three pricing tiers, and a personalised viewing checklist based on the car's age, mileage, and history.
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Related reading
- Your Car History Check Is Missing Half the Picture - Why standard HPI checks miss the data that matters most.
- The Real Cost of Buying a Used Car - How to calculate the true cost before you buy, not after.
- The UK Used Car Trade Has a Data Problem - How dealers and warranty companies can use this data.
Methodology
The analysis uses MOT bulk data published by the Department for Transport covering test years 2020 to 2024. The full dataset contains 199,960,681 individual MOT tests across 3,868 unique vehicle models. Failure rates are calculated per model per mileage band and compared against the national average failure rate for the same failure category across all vehicles tested in the same period. All anomaly findings cited in this article carry a "high confidence" rating, meaning the model sample size is sufficient to draw statistically meaningful conclusions. Model-specific findings with sample sizes below 500 are not included in the above analysis.
Defect rates cited include all MOT annotations for the relevant defect code, including advisories, minor defects, and failures. They represent the frequency at which a defect is noted by a tester, not necessarily the rate at which it causes an outright MOT failure.
Frequently Asked Questions
What is the most common MOT failure in the UK?
Based on our analysis of nearly 200 million MOT tests from 2020 to 2024, suspension component wear is the single biggest category of MOT defects. Specifically, suspension mounting areas and suspension arm bushes account for more total defect annotations than any other category. The most common specific failure is corroded brake pipes, with over 10 million instances in the dataset.
Which car has the highest MOT failure rate?
Among mainstream UK cars, the Ford Ka consistently shows one of the highest defect rates in government MOT data. At 80,000 to 100,000 miles, over 40% of Ford Kas have issues noted at their MOT. 24% are flagged for structural corrosion around the seatbelt anchor points at higher mileages, which is nearly 30 times the UK average.
At what mileage do most cars start failing their MOT?
Government data shows that 60,000 to 80,000 miles is a critical threshold for used car buyers. Suspension components, bushes, and brake systems all show increased defect rates at this mileage. It is also the mileage at which many used cars change hands, which is worth considering when buying.
Do electric cars fail their MOT?
Yes. While electric cars avoid combustion-related failures, they still require MOT tests for suspension, brakes, tyres, lights, and other components. The Tesla Model S, for example, shows a tyre pressure monitoring system failure rate 18 times the UK average at higher mileages (120,000 to 150,000 miles). EVs have a different maintenance profile, not a zero-maintenance one.
Where does this MOT data come from?
All data in this analysis comes from MOT bulk data published as open data by the Department for Transport under the Open Government Licence v3.0. The dataset covers 199,960,681 individual MOT tests from 2020 to 2024 across 3,868 unique vehicle models.