Diesel BMW 420: MOT pass rate
84.4% of diesel BMW 420s pass the MOT first time, measured across 41,928 DVSA tests on that fuel type alone. Average mileage at test was 75,623.
Diesel against the other BMW 420 versions
| Fuel | Pass rate | Tests |
|---|---|---|
| Diesel | 84.4% | 41,928 |
| Petrol | 87.1% | 20,942 |
| All BMW 420 | 85.3% | 62,870 |
Why the fuel type changes the number
Diesels carry DPFs, EGR valves and stricter smoke limits, so emissions and exhaust faults account for failures petrol cars never see.
On the BMW 420 specifically, petrol is the strongest at 87.1%, and this diesel version sits 0.9 points below the 85.3% model average.
What it means if you are buying one
There is little to choose between fuel types on this model, so decide on running costs and mileage rather than MOT record. Buying a damaged one? run it through the analyzer, check the exact car, decode the VIN and check the mileage before you bid.
Mileage is part of the answer
The average diesel BMW 420 had covered 75,623 miles at test, against 48,201 for the petrol. That is a shade above the middle of the range, still ordinary wear rather than a red flag, but worth checking against the service book for the car's age.
Fuel type and mileage are tangled together: diesels are usually bought by higher-mileage drivers, so some of any gap between fuels is the miles rather than the engine. The per-year figures on the BMW 420 page separate age from fuel if you want to isolate one.
Most common MOT failures on a diesel BMW 420
- Any fracture or welding defect on a wheel, 0.5% of tests (8.48x the national rate for this defect)
- A wheel with a loose or missing wheel nut, bolt or stud, 0.8% of tests (2.74x the national rate for this defect)
- Number plate does not conform to the specified requirements, 0.5% of tests (2.49x the national rate for this defect)
- A tyre has a lump, bulge or tear caused by separation or partial failure of its structure. This includes any lifting of the tread rubber, 0.4% of tests (2.14x the national rate for this defect)
- A tyre cords visible or damaged, 3.2% of tests (1.93x the national rate for this defect)
- A shock absorber damaged to the extent that it does not function or showing signs of severe leakage, 1.7% of tests (1.81x the national rate for this defect)
- A tyre seriously damaged, 4.3% of tests (1.53x the national rate for this defect)
- Tyre tread depth not in accordance with the requirements, 3.6% of tests
- a brake lining or pad worn below 1.5mm, 1.7% of tests
- Windscreen washers not working or not providing sufficient fluid to clear the windscreen, 1.3% of tests
From 42,109 DVSA-tracked diesel BMW 420 tests, 2024, split out from the BMW 420's other fuel types. DVSA testers marked 10.75% of these flagged defects as "dangerous", against 5.11% nationally. See which fuel type fails on the most dangerous defects nationally for how that compares across the whole fleet.
Most common MOT advisories on a diesel BMW 420
Flagged but doesn't fail the car, a different list from the failures above.
- Free play in the steering, measured at the rim of the steering wheel is excessive, 0.3% of tests (1.45x the national rate for this defect)
- Tyre tread depth not in accordance with the requirements, 33.1% of tests (1.24x the national rate for this defect), also fails
- a brake lining or pad worn below 1.5mm, 10.5% of tests, also fails
- Brake disc or drum excessively weakened, insecure or fractured, 9.6% of tests
- A tyre seriously damaged, 6.2% of tests, also fails
- A suspension pin, bush or joint excessively worn, 5.2% of tests
- A shock absorber damaged to the extent that it does not function or showing signs of severe leakage, 3.6% of tests, also fails
- Brake disc or drum significantly and obviously worn, 3.4% of tests
- Fluid leaking excessively and likely to harm the environment or to pose a safety risk to other road users, 2.6% of tests
- Number plate inscription missing or illegible, 1% of tests
From 42,109 DVSA-tracked diesel BMW 420 tests, 2024.
Other BMW 420 fuel types
- Petrol BMW 420 - 87.1%