Mercedes-Benz B-Class MOT pass rate & common failures
The Mercedes-Benz B-Class appears in 429,942 MOT tests spanning model years 1991–2025, and 81.8% of them passed. Against MPVs of a similar age (20.7% fail rate), the B-Class comes out 2.4pp better. Its most common failure areas are lighting & signalling, suspension and tyres.
Best and worst B-Class years
Ranked across B-Class years with at least 1,000 tests. Older cars fail more simply because they are older — compare years close together in age before drawing conclusions.
What the MOT record shows
Not every year is equal — 93.6% of 2022 examples pass against 72.6% of 2006 ones.
No single area dominates — lighting & signalling (8.2%) and suspension (6.7%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are coil spring, headlamp aim and washers — coil spring alone was recorded 14,157 times.
Mileage is the strongest signal on the record: 7.3% of 0-30k cars fail, rising to 28.9% once past 150k — 4.0× the risk.
Split by fuel, diesel examples fail 11.0pp more often than hybrid ones (18.5% vs 7.5%) — worth weighing if you have a choice.
Advisories point at the next bill rather than this one: tyres was flagged on 25.4% of tests without failing them.
The trend is worsening — 17.3% of tests failed in 2021 against 18.9% in 2025, the usual pattern as a fleet ages.
How it compares
Versions & engines
MOT records broken out by the engine designations buyers actually search for.
By model year
Every B-Class model year with a usable sample. Years with their own detailed report are linked.
| Year | Tests | Pass rate | Fail rate | Most common failure |
|---|---|---|---|---|
| 2005 | 3,546 | 73.0% | 27.0% | Lighting & signalling |
| 2006 | 16,266 | 72.6% | 27.4% | Lighting & signalling |
| 2007 | 20,165 | 73.0% | 27.0% | Lighting & signalling |
| 2008 | 25,457 | 72.7% | 27.3% | Suspension |
| 2009 | 30,409 | 74.3% | 25.7% | Lighting & signalling |
| 2010 | 31,153 | 75.1% | 24.9% | Lighting & signalling |
| 2011 | 23,983 | 75.4% | 24.6% | Lighting & signalling |
| 2012 | 36,242 | 80.5% | 19.5% | Suspension |
| 2013 | 43,034 | 82.4% | 17.6% | Lighting & signalling |
| 2014 | 49,156 | 83.6% | 16.4% | Lighting & signalling |
| 2015 | 32,705 | 86.2% | 13.8% | Tyres |
| 2016 | 30,367 | 87.8% | 12.2% | Tyres |
| 2017 | 31,974 | 88.7% | 11.3% | Tyres |
| 2018 | 21,901 | 90.2% | 9.8% | Tyres |
| 2019 | 18,488 | 92.7% | 7.3% | Tyres |
| 2020 | 9,578 | 93.2% | 6.8% | Tyres |
| 2021 | 3,947 | 93.5% | 6.5% | Tyres |
| 2022 | 1,517 | 93.6% | 6.4% | Tyres |
| 2023 | 38 | 100.0% | 0.0% | - |
Most common failures (all years)
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 8.2% | 35,439 |
| 2 | Suspension | 6.7% | 28,910 |
| 3 | Tyres | 5.6% | 24,086 |
| 4 | Brakes | 5.0% | 21,412 |
| 5 | Visibility | 3.2% | 13,857 |
| 6 | Body, structure & corrosion | 2.5% | 10,592 |
| 7 | Emissions & environmental | 2.4% | 10,246 |
| 8 | Seat belts & restraints | 1.2% | 4,974 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Coil spring | 14,157 |
| 2 | Headlamp aim | 12,848 |
| 3 | Washers | 9,552 |
| 4 | Joints | 9,139 |
| 5 | Linkage ball joint dust cover | 8,348 |
| 6 | Registration plate lamp(s) | 8,295 |
| 7 | Ball joint | 8,195 |
| 8 | Rigid brake pipes | 8,054 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 25.4% | 109,359 |
| 2 | Brakes | 23.7% | 101,843 |
| 3 | Suspension | 10.9% | 46,964 |
| 4 | Other defects | 10.2% | 43,892 |
| 5 | Lighting & signalling | 4.4% | 18,997 |
| 6 | Body, structure & corrosion | 4.0% | 17,280 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 66,800 | 7.3% |
| 30-60k | 127,683 | 13.7% |
| 60-90k | 122,821 | 21.1% |
| 90-120k | 74,420 | 25.8% |
| 120-150k | 28,131 | 27.9% |
| 150k+ | 9,864 | 28.9% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 282,330 | 18.5% |
| Petrol | 144,174 | 17.9% |
| Electric | 2,314 | 12.1% |
| Hybrid | 1,124 | 7.5% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 82,388 | 17.3% |
| 2022 | 86,056 | 17.5% |
| 2023 | 88,277 | 18.3% |
| 2024 | 87,514 | 19.0% |
| 2025 | 85,707 | 18.9% |
What to check before buying a Mercedes-Benz B-Class
- Lighting & signalling (8.2% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (6.7% of tests): Worn drop links, bushes, springs or shocks — listen for knocks over bumps and check for uneven tyre wear. Typical repair: £150–£450 per corner.
- Tyres (5.6% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
What is the MOT pass rate for the Mercedes-Benz B-Class?
81.8% of the 429,942 Mercedes-Benz B-Class MOT tests in this dataset passed, an 18.2% fail rate, across model years 1991–2025.
What does the Mercedes-Benz B-Class most often fail its MOT on?
Lighting & signalling, recorded in 8.2% of tests, then suspension (6.7%).
Which B-Class years are best and worst for MOT results?
2022 has the best pass rate at 93.6% and 2006 the weakest at 72.6%, from 1,517 and 16,266 tests respectively.
How much does mileage affect B-Class MOT results?
Fail rates run at 7.3% for cars in the 0-30k band and 28.9% for 150k+, a 21.6-point difference.
Is the hybrid or diesel B-Class more reliable at MOT time?
On MOT-testable defects the hybrid fails 7.5% of the time against 18.5% for the diesel. This covers testable items only, not engine or gearbox reliability.
Methodology & source. Based on 429,942 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.