Is old really gold?

Each new 3 Series generation fails its MOT less often than the last

We've all heard the saying 'they don't make 'em like they used to', but have you ever questioned the credibility of that proverb?

The plot below shows MOT fail rate over vehicle age, split by generation. At the same age, each newer generation fails less often: at 13 years old, the E46 fails about 43% of tests, the E90 about 31% and the F30 about 26%.

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How to read it

Each point is the share of first MOT tests at that age that ended in a fail. The shaded band is the 95% confidence interval: wide bands mean few tests, so treat those points with caution. Click a generation in the legend to hide or show it. The E30 and older group starts hidden because its samples are small.

Why it's harder than it looks

• Survivorship. Old cars still being tested are the ones that survived. Neglected cars have already been scrapped, so fail rates at high ages look better than the cars really were.
• Same age isn't the same year. An E46 was 13 around 2018; an F30 turns 13 around 2025. UK average annual mileage has been falling for about two decades, so newer cars are likely to have less wear, and hence a lower failure rate. So "newer generations fail less" is measured, but "newer cars are better built" is not strictly proven by this alone.
• Messy model names. The DVSA data records the 3 Series under hundreds of different labels, from "3 SERIES" to "320D M SPORT". Every one has to be mapped to the right model before any counting starts.

Method

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