Performance by cohort

3 year bands · 62,765 tests

Pass rate climbs 5.1 points across the cohorts — newer S Class examples clear the test more reliably than the early cars.

Pre-2018 cohort 52,240

Pass

85.4%

Fail

11.1%

PRS

2.9%

Avg mileage at test

97,287 mi

2018–2020 cohort 10,357

Pass

93.4%

Fail

5.1%

PRS

0.9%

Avg mileage at test

69,824 mi

2021+ cohort 168

Pass

90.5%

Fail

8.3%

PRS

0.6%

Avg mileage at test

31,269 mi

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

Generations on file · 6

Mercedes Benz S Class · UK market

Mercedes Benz S Class 1979-1991 — 1979–1991

Mercedes Benz S Class 1991-1998 — 1991–1998

Mercedes Benz S Class 1998-2005 — 1998–2005

Mercedes Benz S Class 2005-2013 — 2005–2013

Mercedes Benz S Class 2013-2020 — 2013–2020

Mercedes Benz S Class 2020-now — 2020–now

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

The picture

Mercedes Benz S Class: solid MOT record across 31,423 tests

The Mercedes Benz S Class 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 31,423 tests puts this car on a 83.5% first-time pass rate, above the UK fleet average. Average mileage at test is 89,098 miles. The most common fail item is worn suspension pin or bush, followed by cracked or discoloured windscreen.

The Mercedes S-Class is a superb piece of engineering and a genuine symbol of success. It has a luxurious interior full of the latest technology, plus a wonderful ride that makes you feel like you are cruising in a private jet.

For used buyers, the S Class'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 42–50

A high-group car — insurance costs will be significantly above average. 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 →

42–50

out of 50

Compare quotes →

Top ten reasons for rejection.

Filter failures:

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

01

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

1,252 occurrences · 2.0% of tests
02

A suspension pin, bush or joint excessively worn

1,134 occurrences · 1.8% of tests
03

Tyre tread depth not in accordance with the requirements

1,006 occurrences · 1.6% of tests
04

A suspension joint dust cover severely deteriorated

680 occurrences · 1.1% of tests
05

A rear registration plate lamp or light source missing or inoperative in the case of multiple lamps or light sources

586 occurrences · 0.9% of tests
06

A tyre cords visible or damaged

508 occurrences · 0.8% of tests
07

Brake pipe damaged or excessively corroded

427 occurrences · 0.7% of tests
08

A suspension pin, bush or joint excessively worn

386 occurrences · 0.6% of tests
09

A tyre seriously damaged

380 occurrences · 0.6% of tests
10

Headlamp reflector or lens slightly defective

314 occurrences · 0.5% 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 4 failures

£228–£610

If every one of this S Class'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 8.0-point gap between bands means the year you buy Mercedes Benz S Class has a real effect on what turns up at the garage.

Best band to buy

93.4%

2018–2020 registration

the 2018–2020 band climbs to 93.4% — a 8.0-point improvement. Tests in this band average 69,824 miles — roughly 27K miles fewer on the clock than the older band. Failures here are mostly wear items: tread depth below requirements of 1.6mm, damaged but not adversely affecting driver's view — the structural issues that drag down older examples don't appear in the top-10 for this band. The stricter post-2018 MOT test rules meant manufacturers had to tighten up emissions and electrical checks, but this band still shows far fewer major failures on suspension and bodywork than the older fleet.

Band to be cautious about

85.4%

Pre-2018 registration

On the older band (pre-2018), the data shows a 85.4% pass rate against a fleet average of 93.4% on the newer band. The main culprits logged at test: damaged but not adversely affecting driver's view, ball joint excessively worn, and tread depth below requirements of 1.6mm. Average mileage on test for this band is 97,287 miles — high-mileage wear items are a recurring theme.

Best band to buy: 2018-2020 (93.4% first-time pass). Worst band to avoid: pre-2018 (85.4% pass). That's a 8.0-point spread across 52,240 older tests and 10,357 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

Item 02 · Amazon UK

H7 / W21W bulb pack

A spare-bulb kit lives in the boot. Test morning is not the time to find your stop-lamp's gone.

Search Amazon UK

My Motor World · affiliate

Parts & supplies for this fix

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

Denso

Denso W14E Spark Plug (Single)

£1.09

View at My Motor World →

Denso

Denso W16EX-U Spark Plug (Single)

£1.09

View at My Motor World →

Denso

Denso W16FSR Spark Plug (Single)

£1.09

View at My Motor World →

Denso

Denso W9LM-US Spark Plug (Single)

£1.09

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 →

Owner reports · Honest John

What owners actually report.

Verbatim faults logged by owners on honestjohn.co.uk over recent years. We didn't summarise — these are the words people typed in.

Where it falls short

Expensive, severe depreciation and too much technology for some.

Recall history

65 UK recalls on record.

The S Class has 65 official UK vehicle recalls covering defect details, remedies, and affected build dates.

See all recalls

Buying or keeping a S Class?

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 S Class 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.