Performance by cohort

3 year bands · 141,330 tests

Pass rate climbs 7.0 points across the cohorts — newer 420 examples clear the test more reliably than the early cars.

Pre-2018 cohort 102,172

Pass

86.4%

Fail

10.9%

PRS

2.3%

Avg mileage at test

75,655 mi

2018–2020 cohort 38,426

Pass

89.1%

Fail

8.9%

PRS

1.6%

Avg mileage at test

43,324 mi

2021+ cohort 732

Pass

93.4%

Fail

5.6%

PRS

1.0%

Avg mileage at test

28,303 mi

Cohort = vehicle's first-registration year band. Same model, different generations of build.

Generations on file · 2

BMW 420 · UK market

Photos: Wikimedia Commons · CC BY-SA / CC BY / public domain.

The picture

BMW 420: solid MOT record across 71,832 tests

The BMW 420 is a diesel-powered car sold in the UK market across multiple generations, covering a broad date range in the test population.

MOT data from 71,832 tests puts this car on an 85.6% first-time pass rate, well above the UK fleet average. Average mileage at test is 58,580 miles. The most common fail item is tyre tread below the legal limit, followed by tyre with exposed cords.

For used buyers, the 420's pass rate suggests it clears the MOT with fewer surprises than most — but the top failure items above are still worth a pre-purchase inspection, particularly on higher-mileage examples.

ABI Insurance Group

Group 28–40

Above average — worth comparing quotes before buying. Lower groups cost less to insure; UK fleet average is around Group 22.

Source: ABI Group Rating Panel · administered by Thatcham Research · groups cover standard variants; performance trims may sit higher. Browse all insurance groups →

28–40

out of 50

Compare quotes →

Top ten reasons for rejection.

Filter failures:

Hide wear items to see the model's real defects.

01

Tyre tread depth not in accordance with the requirements

2,422 occurrences · 1.7% of tests
02

A tyre cords visible or damaged

2,247 occurrences · 1.6% of tests
03

Windscreen or window damaged or seriously discoloured but not adversely affecting driver's view

2,222 occurrences · 1.6% of tests
04

A tyre seriously damaged

1,652 occurrences · 1.2% of tests
05

A tyre seriously damaged

1,458 occurrences · 1.0% of tests
06

a brake lining or pad worn below 1.5mm

1,306 occurrences · 0.9% of tests
07

A shock absorber damaged to the extent that it does not function or showing signs of severe leakage

1,050 occurrences · 0.7% of tests
08

Wiper blade defective

769 occurrences · 0.5% of tests
09

Windscreen washers not working or not providing sufficient fluid to clear the windscreen

714 occurrences · 0.5% of tests
10

A wheel with a loose or missing wheel nut, bolt or stud

603 occurrences · 0.4% of tests

Counts cover Major and Dangerous defects logged at test. Advisory items excluded so this shows why a car was rejected, not just what the tester flagged in passing.

Worst-case fix budget · top 2 failures

£120–£190

If every one of this 420's most-logged Major fails hit at the same MOT, that's the real-world UK garage range. Reality is usually one or two items, not all of them. Open the estimator →

Try the calculator

Build your own retest budget.

Year-band analysis

Best year to buy. Worst to avoid.

First-time MOT pass rate split by registration band. A 7.0-point gap between bands means the year you buy BMW 420 has a real effect on what turns up at the garage.

Best band to buy

93.4%

2021+ registration

the 2021-on band climbs to 93.4% — a 7.0-point improvement. Tests in this band average 28,303 miles — roughly 47K miles fewer on the clock than the older band. Failures here are mostly wear items: has a cut in excess of the…, has ply or cords exposed — the structural issues that drag down older examples don't appear in the top-10 for this band. Post-2020 examples are early in their MOT life and generally show the cleanest records.

Band to be cautious about

86.4%

Pre-2018 registration

On the older band (pre-2018), the data shows a 86.4% pass rate against a fleet average of 93.4% on the newer band. The main culprits logged at test: tread depth below requirements of 1.6mm, damaged but not adversely affecting driver's view, and has ply or cords exposed. Average mileage on test for this band is 75,655 miles — high-mileage wear items are a recurring theme.

Best band to buy: 2021+ (93.4% first-time pass). Worst band to avoid: pre-2018 (86.4% pass). That's a 7.0-point spread across 102,172 older tests and 732 newer ones — year of build makes a material difference on this model.

Year-spread leaderboard →

Tools that pre-empt a retest.

Picked against this car's top failure patterns. Affiliate links to Amazon UK — we earn a small cut at no cost to you. Disclosed up-front, doesn't shape the data.

Item 01 · Amazon UK

Digital tyre-tread depth gauge

Five quid for a gauge beats £150 for a retest. UK MOT minimum is 1.6mm — most testers fail anything below 2mm to be safe.

Search Amazon UK

My Motor World · affiliate

Parts & supplies for this fix

Affiliate links — small commission, no extra cost to you.

Summit

Summit ADRG-640 BMW Replacement Stick-On Tinted Mirror Glass LHS

£10.99

View at My Motor World →

Summit

Summit ADRG-904 BMW Replacement Stick-On Tinted Mirror Glass RHS

£10.99

View at My Motor World →

Summit

Summit ADRG-905 BMW Replacement Stick-On Tinted Mirror Glass LHS

£10.99

View at My Motor World →

Draper Expert

Draper Expert Oil Filter Socket for Audi, BMW, Mercedes-Benz, Porsche and VW

£18.69

View at My Motor World →

Click Mechanic · affiliate

Book a mobile mechanic

Affiliate links — small commission, no extra cost to you.

Mobile mechanic · UK-wide

Book a mechanic at your door.

Fixed-price quotes upfront. No garage needed. Click Mechanic sends a vetted local mechanic to you — home, work, or roadside.

Get a quote →

Buying or keeping a 420?

Use the failure ranking as a pre-test checklist or a haggling lever. Treat the headline pass rate as a fleet-wide trend, not a guarantee on any individual car.

If you own a 420 and your last MOT looked nothing like the ranked failures above, that's normal — individual cars vary widely. The ranking shows the patterns testers flag most often across the country.