Mercedes-Benz B-Class — Common MOT Faults
Model-level fault breakdown for the Mercedes-Benz B-Class (2005–present): top failure categories, dangerous defect and retest rates, mileage benchmarks, and an AI-calculated reliability score.
Mercedes-Benz B-Class fault snapshot: first-time MOT pass rate 79.8% (failure rate 20.2%), ranks above the UK average of 64%. Dangerous defect rate 1.7%, retest rate 13.5%. Composite reliability score 75/100 (good). Top failure category: lamps, reflectors and electrical equipment at 15.5% of tests.
Mercedes-Benz B-Class · reliability score
75/100
MOT Checkup reliability score: Good · combines pass rate, dangerous defect rate and retest rate.
79.8%
vs UK 64%
1.7%
13.5%
Top MOT failure categories — Mercedes-Benz B-Class
Categories most likely to trigger an MOT failure on the Mercedes-Benz B-Class. The first three account for the majority of fails.
Lamps, reflectors and electrical equipment
Suspension
Brakes
Tyres
Exhaust, fuel and emissions
Where on the car faults cluster
Front
31%
Rear
28%
Offside
20%
Mileage benchmarks — Mercedes-Benz B-Class
From ages 3 to 5, average mileage on a Mercedes-Benz B-Class rises from around 22,000 miles to 38,000 miles — about 8,000 miles a year, which is in line with the UK average use pattern. A specific car well below or above these averages warrants extra scrutiny — very low mileage on an older car can mean infrequent maintenance just as easily as low use.
Age 3
22,000 mi
Age 5
38,000 mi
Age 10
72,000 mi
Run a free MOT check on this Mercedes-Benz B-Class
Enter the registration to see the actual MOT history for the car you’re looking at — pass/fail, advisories, dangerous defects, mileage at every test. Free and instant.
Free MOT history check at /free-mot-check.
Pre-purchase checklist for a Mercedes-Benz B-Class
- Pull the MOT history first. A pattern of repeat advisories in the same category (e.g. suspension knock noted on three tests in a row) usually means a deferred repair waiting for you.
- Sanity-check the mileage. Compare what’s on the odometer with the readings logged at each MOT. Any backward step or implausibly large jump is a red flag.
- Inspect the top failure points yourself. For this model the cluster is lamps, reflectors and electrical equipment and suspension — both are easy to assess in a short test drive.
- Ask for the last service record. A Mercedes-Benz with consistent dealer or independent service stamps will normally outperform the model-average pass rate of 79.8%.
Compare and explore
Mercedes-Benz B-Class MOT check
Free registration lookup for this model.
Mercedes-Benz reliability
Brand-wide reliability profile and model ranking.
Mercedes-Benz B-Class repair costs
Indicative repair costs for the common faults above.
Volkswagen Polo — common faults
Sibling page at a similar pass rate (79.8%).
Audi A4 — common faults
Sibling page at a similar pass rate (79.8%).
SEAT Leon — common faults
Sibling page at a similar pass rate (79.8%).
Mercedes-Benz B-Class — FAQ
Is the Mercedes-Benz B-Class reliable for MOT?
What are the most common MOT failures on a Mercedes-Benz B-Class?
What's the dangerous defect rate on a Mercedes-Benz B-Class?
How do I check a specific Mercedes-Benz B-Class's MOT history?
Check the MOT history of a Mercedes-Benz B-Class
Free, instant lookup. Every test result, advisory and mileage reading since 2005.
Source: MOT Checkup reliability dataset. Reliability score is a composite metric blending first-time pass rate, dangerous defect rate and retest rate — see /methodology for the formula. Individual cars vary considerably; the registration-level MOT history is the canonical record.