Mercedes-Benz 420: MOT pass rate and reliability data

The Mercedes-Benz 420 passes its MOT first time more often than the average UK car, by 4.1 percentage points. These figures come from the DVSA's full year of anonymised MOT results, covering 594 individual Mercedes-Benz 420 tests. Nothing here is an estimate or a survey.

The numbers

First-time pass rate80.8%
UK national average76.7%
Difference+4.1 points
Tests analysed594
Average mileage at test100,326 miles
Average year of manufacture1988
Reliability rank1,414 of 2,005 models

What this means if you are buying one

A 80.8% first-time pass rate means roughly 19 in every 100 Mercedes-Benz 420s presented for MOT fail on the first attempt. That is better than average, so a well-kept example is a reasonably safe used buy. The average Mercedes-Benz 420 tested had covered 100,326 miles and was built around 1988.

What this means at salvage auction

Pass rate is a proxy for what a car costs to keep on the road. On a Mercedes-Benz 420 bought as a repairable salvage, the mechanical side is less likely to spring surprises, so your repair estimate should hold up reasonably well.

Before you bid: run the lot through the analyzer, check the car's own record, check the mileage, decode the VIN, and if it carries a marker use the write-off value calculator. Or compare it against another model.

Looking at a specific Mercedes-Benz 420 rather than the model in general? The free check covers its MOT and mileage history, and the full HPI report confirms the insurance write-off category, outstanding finance and whether it is recorded stolen, from licensed data for 5 credits. Already own one that has been damaged? Work out whether fixing it beats selling it with the repair or scrap calculator, and see what damaged Mercedes-Benz 420s actually sold for at UK salvage auction.

Most common MOT failures on a Mercedes-Benz 420

  1. Emissions levels exceed default limits, 1.3% of tests (4.52x the national rate for this defect)
  2. An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning, 1.2% of tests (3.54x the national rate for this defect)
  3. Warning device shows system malfunction, 1.1% of tests (3.47x the national rate for this defect)
  4. A suspension joint dust cover missing or no longer prevents the ingress of dirt etc, 4.2% of tests (3.13x the national rate for this defect)
  5. Vehicle structure corroded to the extent that the rigidity of the assembly is seriously reduced, 1.1% of tests (3.11x the national rate for this defect)
  6. Significant brake effort recorded with no brake applied indicating a binding brake, 2.1% of tests (2.71x the national rate for this defect)
  7. The strength or continuity of the load bearing structure within 30cm of any sub-frame, spring or suspension component mounting (a 'prescribed area') is significantly reduced or inadequately repaired, 2% of tests (2.42x the national rate for this defect)
  8. Exhaust system leaking or insecure, 1.8% of tests (2.32x the national rate for this defect)
  9. A headlamp or light source missing, inoperative or more than ½ not functioning in the case of LED, 1.8% of tests (1.97x the national rate for this defect)
  10. The aim of a headlamp is not within limits laid down in the requirements, 3.4% of tests (1.93x the national rate for this defect)

From 1,590 DVSA-tracked Mercedes-Benz 420 tests, 2024. DVSA testers marked 3.1% of these flagged Mercedes-Benz 420 defects as "dangerous", meaning the tester judged the car unsafe to drive away, against 4.97% nationally.

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All 2,005 models ranked by MOT pass rate