Bmw 520 vs Bmw M635: reliability comparison
MOT pass rates, common faults and mileage compared from real UK MOT data.
Bmw 520
78%
MOT pass rate · 156,398 vehicles
Bmw M635
83%
MOT pass rate · 8 vehicles
Verdict: On MOT pass rate the Bmw 520 (78%) and Bmw M635 (83%) are very close — weigh the individual measures below, and remember condition depends on age, mileage and upkeep.
Head to head
| Measure | Bmw 520 | Bmw M635 |
|---|---|---|
| MOT pass rate | 78% | 83% ✓ |
| MOT failure rate | 22% | 17% ✓ |
| Faults & advisories per test | 1.6 ✓ | 2.1 |
| Dangerous-fault share | 3% | 0% ✓ |
| Average mileage | 134,460 mi | 113,319 mi |
| Sample size (vehicles) | 156,398 | 8 |
Most common faults
Bmw 520
- Nearside Rear Tyre worn close to the legal limit (4.1.E.1)
- Offside Rear Tyre worn close to the legal limit (4.1.E.1)
- Offside Rear Tyre worn close to legal limit/worn on edge (5.2.3 (e))
- Nearside Rear Tyre worn close to legal limit/worn on edge (5.2.3 (e))
- Under-trays fitted obscuring some underside components
- Nearside Front Tyre worn close to legal limit/worn on edge (5.2.3 (e))
Bmw M635
- Front Brake disc worn, pitted or scored, but not seriously weakened (1.1.14 (a) (ii))
- Rear Brake disc worn, pitted or scored, but not seriously weakened (1.1.14 (a) (ii))
- Nearside Front Brake pipe corroded, covered in grease or other material (1.1.11 (c))
- Offside Front Headlamp not working on dipped beam (4.1.1 (a) (ii))
- Both seats play
- Child Seat fitted not allowing full inspection of adult belt
Reliability FAQ
On MOT pass rate the Bmw 520 (78%) and Bmw M635 (83%) are very close — weigh the individual measures below, and remember condition depends on age, mileage and upkeep.
Full Bmw 520 report Full Bmw M635 report Most reliable cars
Pass rates are computed over completed (pass/fail) MOT tests. Reliability also depends on age, mileage and upkeep — see each model's page for the full picture.