Mercedes-Benz 420 MOT reliability

Mercedes-Benz 420s passed their MOT first time 80% of the time across 571 tests in 2025.

First-time pass rate

80%

MOTs analysed

571

Still licensed (GB)

–

Body type

Sedan

Pass rate by year of first registration

Older cars fail more often, so compare a car with others of the same age. Years with very few MOTs can show extreme pass rates, even 0% or 100%, so give more weight to years with more tests.

In detail:

First registered

1998 petrol

2 MOTs

These figures come from only 2 MOT tests. With so few cars, a single pass or fail changes the percentages a lot, so treat them as a rough guide rather than a true average.

Passed first time 50%. Typical mileage 73,278 (most between 63,868 and 82,688).

2021: 50% → 2022: 100% → 2023: 100% → 2024: 100% → 2025: 50%

Most common failures

Catalyst emissions: Lambda reading after 2nd fast idle outside specified limits (50.0%)
Catalyst emissions: carbon monoxide content at idle exceeds default limits (50.0%)

Where 1998 420s fail

Exhaust, emissions & leaks

50.0%

Looking at a particular car?

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Based on 2025 initial MOT tests in DVSA's anonymised MOT dataset (cars and light vans). Contains public sector information licensed under the Open Government Licence v3.0. Model details: Vehicle data by VehiclesDB.