BMW 3 Series vs Mercedes-Benz C-Class: which fails its MOT less?
Allowing for age, the BMW 3 Series fails its MOT less often than the Mercedes-Benz C-Class.
- less often than the Mercedes-Benz C-Class, at the same age
- 8.0%less often than the Mercedes-Benz C-Class, at the same age
MOTs passed in 2024: BMW 3 Series 79.7%, Mercedes-Benz C-Class 78.0%
Both fail less often than normal for their age.
Data: DVSA MOT results · 2024 · 864,186 tests
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Which fails less for its age?
Allowing for age, the BMW 3 Series fails less often: MOT Risk Index 80.7 against 87.4 (100 = normal for its age; difference 6.7, 95% CI 6.1–7.3).
Both fail less often than normal for their age.
| Measure | BMW 3 Series | Mercedes-Benz C-Class | Years |
|---|---|---|---|
| Passed at the first attempt, % | 75.1 | 74.1 | 2024 |
| MOT Risk Index (100 = normal) | 80.7 | 87.4 | 2024 |
| 95% interval of the index | 80.4–81.1 | 86.9–87.9 | 2024 |
| Rank among 761 models (1 = fails least for its age) | 263 | 327 | 2024 |
| First tests | 498,596 | 365,590 | 2024 |
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After defects were fixed at the test centre
79.7% of BMW 3 Series tests and 78.0% of Mercedes-Benz C-Class tests passed, including defects fixed during the test. This is a different outcome from passing at the first attempt.
What explains the difference?
The clearest difference is suspension: against its own class and age, the BMW 3 Series runs −6.2 items per 100 tests and the Mercedes-Benz C-Class +2.6, so the BMW 3 Series has 8.7 fewer per 100 tests (95% interval 8.7 to 8.8).
Each model is compared with its own class and age; the fleets can differ in mileage and use.
More detail
Dangerous defects and advisory items
| Measure | BMW 3 Series | Mercedes-Benz C-Class |
|---|---|---|
| Dangerous defects per 100 tests | 12.7 | 11.7 |
| Advisory items per 100 tests | 127.8 | 117.1 |
Source: DVSA MOT bulk data, 2019–2024. A test can record several items. CSV
At what age does one of them fail more?
They change places at age 4: the difference is clear at 13 of 17 ages, and which fails less depends on the age of the car. Across the 4 yearly tests from age 4 to 7, the gaps add up to 2.6 extra failed tests per 100 for the Mercedes-Benz C-Class (a sum of yearly rates, not the chance of one car failing).
| Age | Difference, pp | 95% interval | Reading |
|---|---|---|---|
| 3 | +0.9 | +0.6 to +1.3 | Mercedes-Benz C-Class fails less |
| 4 | −0.7 | −1.0 to −0.3 | BMW 3 Series fails less |
| 5 | −1.0 | −1.3 to −0.7 | BMW 3 Series fails less |
| 6 | −0.7 | −1.0 to −0.3 | BMW 3 Series fails less |
| 7 | −0.2 | −0.6 to +0.1 | not distinguishable |
| 8 | −0.2 | −0.6 to +0.2 | not distinguishable |
| 9 | +0.0 | −0.4 to +0.5 | not distinguishable |
| 10 | −0.4 | −0.9 to +0.0 | not distinguishable |
| 11 | −1.1 | −1.6 to −0.6 | BMW 3 Series fails less |
| 12 | −1.8 | −2.4 to −1.3 | BMW 3 Series fails less |
| 13 | −2.7 | −3.3 to −2.1 | BMW 3 Series fails less |
| 14 | −4.0 | −4.7 to −3.4 | BMW 3 Series fails less |
| 15 | −4.2 | −4.8 to −3.5 | BMW 3 Series fails less |
| 16 | −5.1 | −5.8 to −4.5 | BMW 3 Series fails less |
| 17 | −5.0 | −5.8 to −4.3 | BMW 3 Series fails less |
| 18 | −4.6 | −5.4 to −3.7 | BMW 3 Series fails less |
| 19 | −3.8 | −4.8 to −2.8 | BMW 3 Series fails less |
| Age band | Ages included | BMW 3 Series, % | Mercedes-Benz C-Class, % | Difference, pp | 95% interval | Reading |
|---|---|---|---|---|---|---|
| 3–5 | 3–5 | 12.7 | 13.1 | −0.3 | −0.5 to −0.2 | BMW 3 Series fails less |
| 6–10 | 6–10 | 21.6 | 21.4 | +0.2 | +0.1 to +0.3 | Mercedes-Benz C-Class fails less |
| 11+ | 11–20+ | 34.1 | 36.9 | −2.8 | −2.9 to −2.7 | BMW 3 Series fails less |
Source: DVSA MOT bulk data · Window: 2019–2024 · n = 4,879,443 (initial tests at shared ages) · Method: difference of two proportions per age, Bonferroni-corrected for 17 ages; age bands pool the published ages with an unadjusted 95% interval, and the same car can appear at more than one age, so that interval is somewhat narrow · Updated: 25 Sep 2026 · Release: dvsa-2024-v2 · CSV
Where do their MOT failures diverge?
The clearest difference is suspension: against its own class and age, the BMW 3 Series runs −6.2 items per 100 tests and the Mercedes-Benz C-Class +2.6, so the BMW 3 Series has 8.7 fewer per 100 tests (95% interval 8.7 to 8.8).
| Component group | BMW 3 Series vs its class | Mercedes-Benz C-Class vs its class | Gap, BMW 3 Series minus Mercedes-Benz C-Class | 95% interval | Reading |
|---|---|---|---|---|---|
| Suspension | −6.2 | +2.6 | −8.7 | −8.8 to −8.7 | BMW 3 Series fails less |
| Body, chassis, structure | −5.1 | −3.8 | −1.3 | −1.3 to −1.2 | BMW 3 Series fails less |
| Lamps, reflectors and electrical equipment | −8.1 | −6.9 | −1.2 | −1.3 to −1.2 | BMW 3 Series fails less |
| Noise, emissions and leaks | −1.1 | −0.1 | −0.9 | −1.0 to −0.9 | BMW 3 Series fails less |
| Steering | −2.4 | −1.6 | −0.9 | −0.9 to −0.8 | BMW 3 Series fails less |
| Visibility | −0.8 | −1.4 | +0.6 | +0.5 to +0.6 | Mercedes-Benz C-Class fails less |
Source: DVSA MOT bulk data · Window: 2019–2024 · n = 5,182,871 (initial tests) · Method: each model's failure items per 100 tests against the rate expected for its own class and age; Poisson interval; the age standard leaves the model out and is treated as fixed; items in the same test are treated as independent, so the interval is slightly narrow · Updated: 25 Sep 2026 · Release: dvsa-2024-v2 · CSV
If one fails, which is more likely to fail again?
A failure carries about the same extra risk of failing again on both: 9.5 percentage points on the BMW 3 Series, 9.2 on the Mercedes-Benz C-Class.
| Measure | BMW 3 Series | Mercedes-Benz C-Class |
|---|---|---|
| After a failed test, % | 31.7 | 30.2 |
| After a passed test, % | 22.1 | 21.0 |
| Extra risk carried by a failure, pp | 9.5 | 9.2 |
Source: DVSA MOT bulk data · Window: 2019–2024 · n = 262,044 (tests after a fail) · Method: test chains of the same vehicles; cars sold or scrapped after a fail drop out · Updated: 25 Sep 2026 · Release: dvsa-2024-v2 · CSV
What do six years of MOTs show about the two?
The biggest gap in advisories turning into fails is suspension: 17.1% on the BMW 3 Series against 23.8% on the Mercedes-Benz C-Class failed on the same item at the next MOT.
| Component | BMW 3 Series | Mercedes-Benz C-Class | Difference, pp |
|---|---|---|---|
| Suspension | 17.1 | 23.8 | −6.6 |
| Steering | 5.1 | 10.6 | −5.5 |
| Visibility | 12.5 | 9.3 | +3.2 |
| Lamps, reflectors and electrical equipment | 23.3 | 25.3 | −2.0 |
| Brakes | 13.3 | 11.7 | +1.5 |
| Body, chassis, structure | 6.9 | 6.2 | +0.7 |
| Tyres | 10.5 | 10.0 | +0.5 |
| Road wheels | 2.4 | 2.1 | +0.4 |
| Identification of the vehicle | 2.8 | 2.6 | +0.2 |
| Noise, emissions and leaks | 7.5 | 7.6 | −0.1 |
| Measure | BMW 3 Series | Mercedes-Benz C-Class |
|---|---|---|
| Repaired and passed the same day | 36.0% | 39.0% |
| Passed 1–10 days later | 60.0% | 57.5% |
| Median retest delay | 1.0 days | 1.0 days |
| Failures per 10,000 miles | 0.368 | 0.340 |
| Three-test clean streak | 36.4% | 38.4% |
| Same advisory repeated 3+ times | 31.3% | 27.0% |
Source: DVSA MOT bulk data · Window: 2019–2024 · n = 2,985,382 (tracked advisories) · Method: same vehicles followed to their next ordinary MOT; common publishable components only · Updated: 25 Sep 2026 · Release: dvsa-2024-v2 · CSV
Recalls, other countries and running costs, side by side
DVSA lists 121 recall campaigns matched to the BMW 3 Series and 158 to the Mercedes-Benz C-Class; more campaigns do not by themselves mean a less reliable car. Abroad, compare each model with that country's own average, because pass rates do not carry across rulebooks. Repair bills are catalogue estimates, not quotes.
| Measure | BMW 3 Series | Mercedes-Benz C-Class |
|---|---|---|
| DVSA recall campaigns listed | 121 | 158 |
| Finland Katsastus: fails, % (national average 26.3%) | 32.1 (30,097 inspections) | 35.3 (39,349 inspections) |
| Netherlands APK: fails, % (national average 50.8%) | 49.2 (70,874 inspections) | 48.1 (56,302 inspections) |
| Norway PKK: fails, % (national average 33.7%) | 48.2 (1,305 inspections) | 36.5 (16,299 inspections) |
| Expected MOT repair bill, £ (estimate) | £75 | £74 |
| Repair bill range, £ (catalogue range, not a 95% interval) | £75–£142 | £74–£141 |
Source: DVSA vehicle recalls register (OGL v3.0); Statens vegvesen PKK (CC BY 4.0), Traficom Katsastus (CC BY 4.0), RDW APK (CC0), adapted; UK repair price catalogue · Window: register as published; inspections 2024 · n = 214,226 (inspections abroad) · Method: recall campaigns matched by make and model, licensed-fleet denominator where available; abroad, samples below 500 suppressed and each model set against that country's own average, with no difference taken across countries; repair bill = chance of failing each item × its most common UK repair price, a catalogue estimate · Updated: 25 Sep 2026 · Release: dvsa-2024-v2 · CSV · licences and full notice
How to cite this comparison
MOT Risk Index (2026). BMW 3 Series vs Mercedes-Benz C-Class: MOT statistics 2024 (data release dvsa-2024-v2; full dataset motriskindex-families-2024-v5, DOI 10.5281/zenodo.22975051), updated 25 September 2026. motriskindex.co.uk/compare/bmw-3-series-vs-mercedes-c-class/
How the MOT Risk Index and every figure on this page are calculated: methodology.
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BMW 3 Series vs Mercedes-Benz C-Class: quick answers
Is the BMW 3 Series or the Mercedes-Benz C-Class more reliable?
Allowing for age, the BMW 3 Series fails less often: MOT Risk Index 80.7 against 87.4 (100 = normal for its age; difference 6.7, 95% CI 6.1–7.3).
Does the BMW 3 Series or the Mercedes-Benz C-Class fail more MOTs?
24.9% of BMW 3 Series first tests and 25.9% of Mercedes-Benz C-Class first tests failed in 2024. These raw rates do not allow for age; the MOT Risk Index does.
Which should I buy, the BMW 3 Series or the Mercedes-Benz C-Class?
If MOT reliability decides it, the evidence favours the BMW 3 Series. Still check the individual car's MOT history: these figures describe whole model populations.