Mercedes-Benz C-Class vs Audi A4
Figures updated
The Mercedes-Benz C-Class and Audi A4 are two of the UK's most popular executive cars. We compare the W206 (2021–) C-Class and the B9 (2015–2024) A4 on price, size, boot space, performance, safety and running costs, plus how reliable each has been across 607,049 real MOT tests.
The short answer
The Audi A4 comes out ahead, with lower fuel costs; the Mercedes-Benz C-Class is close on everything else.
- Their boots are much the same size: Mercedes-Benz C-Class 455 litres, Audi A4 460 litres.
- Their MOT records are close: once age and mileage are taken into account, they fail about as often as each other.
- The Audi A4 is the cheapest to fuel: comparing diesel versions, about £191 a year less than the Mercedes-Benz C-Class at 7,500 miles a year.
| Figure | Mercedes-Benz C-ClassW206 (2021–), 4-door saloon | Audi A4B9 (2015–2024), 4-door saloon |
|---|---|---|
| Price and practicality | ||
| Price newUK list prices, across the range | £46,995 to £62,515September 2026 price list | – |
| Body | 4-door saloon | 4-door saloon |
| Seats | 5 | 5 |
| BootSeats up / folded | 455 litres | 460 litres |
| Length | 4,773mm | 4,762mm |
| WidthWithout mirrors | 1,820mm | 1,847mm |
| Height | 1,443mm | 1,387mm |
| Performance | ||
| Power | 218–258 PS | 136–265 PS |
| 0–62mph | 5.9–7.3 sec | 5.5–9.5 sec (best) |
| Safety | ||
| Euro NCAP ratingTests get tougher each year | ★★★★★ (2022) | ★★★★★ (2015) |
| Economy and emissions | ||
| Fuel types | Diesel, Petrol, Plug-in hybrid | Diesel |
| Official economyVersions of this generation | 25.5–62.8 mpg | 54.3–74.3 mpg |
| CO2 | 10–253 g/km | 99–137 g/km |
| Running costs at 7,500 miles a year | ||
| Petrol or hybrid171.5p a litre, today's UK average | £1,531 (38.2 mpg) | – |
| Diesel198.4p a litre | £1,221 (55.4 mpg) | £1,030 (65.7 mpg) (best) |
| Cheapest version to fuelWhichever fuel costs least | £1,221 (diesel) | £1,030 (diesel) |
| Car tax, registered 2001 to 2017Taxed on CO2; newer cars pay a flat £200 | £20 to £790 | £20 to £790 |
| Reliability from real MOT tests | ||
| Reliability score | 120Well above average | 125Well above average (best) |
| Failed MOT first time (ages 3–20) | 25.5% (best) | 27.1% |
| Failed at 3 years old | 13.1% | 11.8% (best) |
| Failed at 5 years old | 13.8% (best) | 14.5% |
| Failed at 10 years old | 27.1% | 26.3% |
| Most common MOT fault | Ball joint (4.5% of tests) | Coil spring (3.6% of tests) |
| Fails more than average on | Nothing stands out | Nothing stands out |
| MOT tests analysed | 362,136 | 244,913 |
| About the cars | ||
| Type | Executive car | Executive car |
| Owners' average miles a year | 8,900 | 9,900 |
| On sale | 2021 on | 2015–2024 |
Green marks the better figure where the difference is more than 3%. Reliability figures cover every version of each model tested in the year. Running costs use the typical official economy of recent versions (WLTP where available); real-world economy is usually a little worse for every car.
More comparisons
Frequently asked questions
›Is the Mercedes-Benz C-Class or the Audi A4 more reliable?
There's little in it. Once age and mileage are taken into account, both fail their MOT about as often as each other (reliability scores 120 and 125, where 100 is average).
›Which is bigger, the Mercedes-Benz C-Class or the Audi A4?
They're almost the same length (4,773mm and 4,762mm). Their boots are much the same: 455 and 460 litres.
›Which is cheaper to run, the Mercedes-Benz C-Class or the Audi A4?
Comparing diesel versions, the Audi A4 costs about £191 a year less to fuel at 7,500 miles (£1,030 against £1,221), using typical official economy and current UK average fuel prices.
›Which is safer, the Mercedes-Benz C-Class or the Audi A4?
Euro NCAP gave the Mercedes-Benz C-Class 5 stars (2022) and the Audi A4 5 stars (2015). Euro NCAP makes its tests tougher every few years, so ratings from different years aren't directly comparable.
›Should I buy the Mercedes-Benz C-Class or the Audi A4?
The Audi A4 comes out ahead, with lower fuel costs; the Mercedes-Benz C-Class is close on everything else. The comparison above sets out price, space, performance, safety, running costs and reliability side by side.
Sources: manufacturers' UK specifications and price lists and Euro NCAP (listed on each model's page); DVSA anonymised MOT tests 2024 (Open Government Licence v3.0); Vehicle Certification Agency car fuel data, © Crown copyright, VCA cannot accept liability for its accuracy; fuel prices from the GOV.UK Fuel Finder scheme. Photos from Wikimedia Commons, credited under each picture.