All generations and engines together · 60,899 MOT tests in the 2025 data · typical mileage at age 7: 50k
Middling for its age among people carriers, and better than most per mile driven. Watch brakes and suspension. A fair used buy, provided its MOT history has no repeating brakes advisories.
Split by first-registration year. Cars registered in a changeover year can belong to either generation.
Owner folklore from forums and the motoring press, with how well each report stands up. Most of it never shows up in an MOT, which is why this section exists at all.
The 7-speed dual-clutch automatic (and the later 8-speed version) can hesitate or lurch pulling away from cold, and some owners report a sudden surge of acceleration around 5-15mph as it shifts from 1st to 2nd. Worse cases develop a judder or clang from the clutch pack, reported anywhere from 18,000 to 68,000 miles, sometimes ending in a full transmission replacement. Mercedes has pushed software updates to the gearbox control unit to calm the hesitation, and specialists advise a transmission oil and filter change every 3 years/38,000 miles rather than relying on it as "sealed for life".
On the early B-Class, the CVT automatic has a history of valve body wear and sensor faults, then outright failure. Owners have reported a secondary speed sensor fault at 30,000 miles (£1,439 repair), valve body failure around 6 years/70,000 miles (£1,250), and complete gearbox failure at 62,000 miles (£4,200 quoted). One of the earliest reported cases, at 43,000 miles, cost £5,355 even after a Mercedes goodwill contribution. Manual cars are unaffected.
A repeated theme among 2011-plate cars: the EIS (electronic ignition switch) module fails and the car simply won't start, with no warning beforehand. The fix is a replacement module, quoted around £500. It hasn't been the subject of a recall or a published fix, it just keeps coming up in owner reports on that model year.
Leaves and road debris can clog the bulkhead vent wells, so water backs up into the battery compartment and soaks the pollen filter instead of draining away; a separate seal can also fail and let water into the spare wheel well. Symptoms are damp carpets, a musty smell, or odd electrical faults after heavy rain. Owners are split on whether it's a design flaw or just needs the drains cleared out once a year, and Mercedes hasn't acknowledged it as a fault.
On CDI diesel engines, glow plugs can corrode and seize into the cylinder head, a problem made worse by lots of short, cold journeys that never let the engine fully warm through. A seized plug that snaps on removal can mean stripping the head to get it out, so cost varies a lot depending on how bad it's got. Doesn't apply to the petrol engines.
The rare electric B250e (sold briefly in the UK) has been reported to drain its 12V battery quickly while charging, leaving the car immobile with a "visit workshop" message on the dash. Main battery pack concerns have been quoted at around £5,000. Only relevant if you're looking at the electric version, which is a small slice of used B-Class stock.
Ranked from this model’s own MOT record, then from what owners report.
Saveable checklistThe physical checks its own defect data says are worth your time, most telling first.
These judge the seller’s upkeep rather than the model, and they are where the haggling money is.
The physical checks its own defect data says are worth your time, most telling first.
These judge the seller’s upkeep rather than the model, and they are where the haggling money is.
The physical checks its own defect data says are worth your time, most telling first.
These judge the seller’s upkeep rather than the model, and they are where the haggling money is.
The physical checks its own defect data says are worth your time, most telling first.
These judge the seller’s upkeep rather than the model, and they are where the haggling money is.
Drawn from the reports above rather than the MOT data. These are the model-specific ones.
Computed from DVSA MOT results, all of Great Britain, 2025. Nothing here is opinion.
Share of tests where each item was recorded. The dark tick is the class average across all tracked models; bars are scaled within each group.
The rows that judge the model rather than its keeper. 19,258 tests in this band.
Tyres, pads and stone chips say more about how the car was driven and maintained than about how it was built.
Same segment (MPVs), best MOT record first. Compare before you shortlist.
Head to head with the other popular cars in its class on reliability and common faults.