BMW 3-Series vs Audi A4: what the MOT record says
The BMW 3-Series and Audi A4 look like the same used-car problem from ten paces: premium German saloons, mostly diesel in the older stock, usually bought by people who tell themselves they are choosing engineering rather than badge. The 2024 public UK MOT record says the headline fight is almost dead level. The useful story is lower down, where the two cars fail in different ways.
Pass-rate split
Across the 2024 public UK MOT record, the BMW 3-Series recorded
The Audi A4 recorded
That is not a knockout. It is a photo finish. The BMW leads by
The BMW still gets the verdict here, but only because the supporting numbers lean its way. It has the bigger sample, the slightly better headline pass rate, a higher average mileage at test, and a stronger older-car cohort. That last bit matters. Most used buyers are not shopping nearly-new A4s and 3-Series models still living under main-dealer care. They are looking at cars that have already seen winter salt, cheap tyres, rushed servicing and tired suspension.
A pass-rate gap this small does not let you ignore the individual car. It does tell you where to start your suspicion.
Where they fail
The BMW 3-Series failure list is a familiar German executive saloon mix: glass, tyres, dampers, lamps and suspension wear. Its top recorded failure reasons in 2024 were:
- Windscreen or window damage or serious discolouration not adversely affecting the driver’s view: 24,779
- Tyre tread depth below requirements: 17,359
- Shock absorber damaged enough not to function, or showing severe leakage: 16,638
- Lamp missing or inoperative: 11,645
- Tyre cords visible or damaged: 11,046
There is a clear split in that list. Some of it is owner neglect: tyres, wipers, lamps, washers. Some of it is age, weight and use: shock absorbers and suspension joints. The 3-Series is often driven as intended. That usually means motorway miles, hard braking, broken urban surfaces and low-profile tyres. None of that is shocking. It does mean a cheap 3-Series with mismatched tyres and vague body control is not a bargain. It is a bill with leather seats.
The Audi A4 has a different smell to its data. Its top recorded failure reasons in 2024 were:
- Windscreen or window damage or serious discolouration not adversely affecting the driver’s view: 14,447
- Transmission shaft constant velocity joint boot severely deteriorated: 13,083
- Tyre tread depth below requirements: 12,816
- Spring or spring component fractured or seriously weakened: 11,789
- Rear registration plate lamp or light source missing or inoperative: 11,431
The Audi’s list is more drivetrain-and-suspension heavy near the top. CV joint boots appear second, another CV boot reason appears sixth, springs sit fourth, suspension bushes and dust covers follow close behind. That is the divide. The BMW’s most prominent mechanical flag is dampers. The A4 pushes you harder towards underside inspection: boots, springs, joints, covers, front-end wear.
Neither car gets a free pass. These are not simple cars, and parts pricing can make a small MOT defect feel less small once labour is added. But the failure pattern is not identical, and that is useful. If you are viewing an A4, clean paint and a stamped book are not enough. You want evidence that split boots, broken springs and suspension wear have not been allowed to stack up. If you are viewing a 3-Series, you want tyre condition, damper condition and brake effort treated as part of the price discussion, not as afterthoughts.
Cohort tells
The age-band split is where the comparison becomes sharper.
For pre-2018 cars, the BMW 3-Series recorded 763,858 tests and passed at 77.98%. The Audi A4 recorded 440,138 tests and passed at 77.38%. That gives the BMW a 0.60-point lead in the older stock. It is not huge, but this is the cohort that matters most to the used market. These are the cars most likely to be on their third or fourth owner, outside dealer maintenance, and old enough for age-related MOT issues to show.
In the 2018-2020 band, the BMW recorded 47,150 tests and passed at 89.73%. The Audi recorded 50,871 tests and passed at 89.47%. Again, BMW edges it, this time by 0.26 points. The samples are similar enough that the comparison feels fair. Both cars look strong here, which fits the age profile: old enough to need tests, not old enough for neglect and fatigue to dominate every result.
The 2021+ band flips the headline. The A4 passed at 93.76% from 577 tests, while the 3-Series passed at 91.15% from 915 tests. That sounds like an Audi win, but the sample is tiny compared with the older cohorts. It is still worth recording because nearly-new buyers care, but it should not outweigh the older-car result.
The lesson is blunt: buy by cohort, not badge myth. A 2019 A4 with clean tyres, no CV boot issues and a tidy test history is a better bet than a neglected 2014 3-Series. But when you average the big older fleets, the BMW is fractionally ahead.
That matters because executive saloons age in expensive ways. They do not usually fall apart through one dramatic defect. They become bad buys when several ordinary wear items arrive at the same time: tyres, dampers, springs, bushes, brakes, lamps and emissions warnings. The MOT record catches that pile-up more honestly than owner reviews do.
Mileage tells
The BMW 3-Series averaged 109,112 miles at test in 2024. The Audi A4 averaged 107,570 miles.
That difference is modest, but it leans with the pass-rate result. The BMW fleet is passing at almost the same rate while carrying slightly higher average mileage. For a used buyer, that is more persuasive than the 0.03-point headline gap on its own. The 3-Series is not winning because it is sheltered. It is doing it with a bigger test count and a marginally higher average mileage at test.
The mileage split also explains why the failure lists look the way they do. At these mileages, tyres are not just consumables; they are evidence. A premium saloon on cheap, mismatched or badly worn tyres usually tells you something about the owner’s appetite for maintenance. Dampers, suspension bushes, CV boots and springs are the same story. They are not rare exotic failures. They are ordinary age-and-use items that become expensive when ignored.
For the BMW, shock absorber failure is the item that should make you slow down. It is third on the whole-model failure list, with 16,638 recorded failures. A tired damper changes braking behaviour, tyre wear and ride control. If a seller says “it just needs an MOT”, that can mean it needs suspension money before it is a proper car again.
For the Audi, the CV boot and spring pattern is the sharper warning. A split boot is often cheap if caught early and ugly if ignored. Dirt gets in, grease gets out, and the joint follows. Springs are also not rare on UK roads, but a fractured spring on an A4 is not something to wave away while paying executive-car money.
The badge does not fail the MOT. The maintenance pattern does.
That is the right way to read this comparison. BMW and Audi owners both buy into the same premium promise. The MOT record shows two cars with almost identical first-time pass rates, but not identical failure paths.
The numbers we trust
This comparison uses the 2024 public UK MOT record held in this project’s mot-2024 dataset. The BMW 3-Series sample is 811,923 tests. The Audi A4 sample is 491,586 tests. Together, that is 1,303,509 recorded tests, which is large enough to make small patterns worth discussing, but not magic.
The pass rate is first-time MOT pass rate in the model-level record. It is not a warranty claim rate. It is not a repair-cost index. It does not know whether the owner fitted premium tyres, serviced on time, ignored warning lights or booked a test with a blown bulb. It does show how often each model cleared the test first time in a very large official record.
There are also model-shape problems. “BMW 3-Series” covers many generations, engines, body styles and use cases. “Audi A4” does the same. A well-kept older 320d and a neglected high-mileage performance-trim car should not be treated as the same risk. The same goes for diesel A4s that have spent their lives on motorways versus tired urban cars with repeated suspension advisories.
That is why the cohort split is essential. Pre-2018 cars dominate both samples: 763,858 BMW tests and 440,138 Audi tests. This is the used-car battlefield. In that band, the BMW is ahead by 0.60 points. In 2018-2020 cars, BMW is ahead by 0.26 points. In the small 2021+ cohort, Audi is ahead. If you are buying nearly new, inspect the car in front of you and do not overread the older fleet. If you are buying the usual used executive saloon, the older cohort should carry more weight.
The practical buying advice is simple. For a BMW 3-Series, check the MOT history for repeated tyre, shock absorber, brake and suspension advisories. Then look at the car with those exact items in mind. Uneven tyre wear, misted dampers, warning lights and weak parking brake performance should all move the price.
For an Audi A4, spend more time underneath. CV boots, driveshaft-related notes, broken springs, suspension dust covers and worn joints are the pattern. A clean A4 with recent suspension work can be a very good used car. An A4 with repeated advisories for boots and joints is asking you to fund deferred maintenance.
The BMW wins by the narrowest headline margin, but the verdict is not soft. The 3-Series has the better older-car pass rate, the slightly higher average mileage at test and the larger sample. That is enough to put it ahead. The A4 is too close to dismiss, and in the newest cohort it looks better, but its failure pattern is less friendly if you are buying older stock without a careful inspection.
The Audi A4 remains a serious used buy, especially if the car is newer or has clean evidence around springs, CV boots and suspension work. But on equal condition, the BMW is the sharper MOT-data pick. Buy the A4 only when the individual history is cleaner than the average and the underside backs it up.