Mercedes-Benz C-Class vs Audi A6
Figures updated
The Mercedes-Benz C-Class and Audi A6 are two of the UK's most popular executive cars. We compare the W206 (2021–) C-Class and the C9 (2025–) A6 on price, size, boot space, performance, safety and running costs, plus how reliable each has been across 484,761 real MOT tests.
The short answer
Pick the Mercedes-Benz C-Class for the lower price, or the Audi A6 for the bigger boot, the better MOT record and lower fuel costs.
- The Mercedes-Benz C-Class is the cheapest to buy new: from £46,995, £7,065 less than the Audi A6.
- The Audi A6 has the biggest boot: 492 litres, 37 more than the Mercedes-Benz C-Class.
- The Audi A6 has the better MOT record. Like for like on age and mileage, the Mercedes-Benz C-Class fails its MOT about 29% more often.
- The Audi A6 is the cheapest to fuel: comparing petrol versions, about £83 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 A6C9 (2025–), 4-door saloon |
|---|---|---|
| Price and practicality | ||
| Price newUK list prices, across the range | £46,995 to £62,515September 2026 price list (best) | from £54,060October 2026 price list |
| Body | 4-door saloon | 4-door saloon |
| Seats | 5 | 5 |
| BootSeats up / folded | 455 litres | 492 litres (best) |
| Length | 4,773mm | 4,999mm |
| WidthWithout mirrors | 1,820mm | 1,875mm |
| Height | 1,443mm | 1,452mm |
| Performance | ||
| Power | 218–258 PS | 204–299 PS (best) |
| 0–62mph | 5.9–7.3 sec | 6.0–8.2 sec |
| Safety | ||
| Euro NCAP ratingTests get tougher each year | ★★★★★ (2022) | ★★★★★ (2024) |
| Economy and emissions | ||
| Fuel types | Diesel, Petrol, Plug-in hybrid | Electric, Hybrid, Petrol, Plug-in hybrid |
| Official economyVersions of this generation | 25.5–62.8 mpg | 36.2–55.4 mpg |
| CO2 | 10–253 g/km | 32–178 g/km |
| Electric range | – | 329–462 miles |
| Running costs at 7,500 miles a year | ||
| Petrol or hybrid171.8p a litre, today's UK average | £1,533 (38.2 mpg) | £1,450 (40.4 mpg) (best) |
| Diesel198.4p a litre | £1,221 (55.4 mpg) | – |
| Electric, charged at home26.3p per kWh standard tariff | – | £548 (4 mi/kWh) |
| Cheapest version to fuelWhichever fuel costs least | £1,221 (diesel) | £548 (electric) |
| Car tax a yearCars registered from April 2017 | £200£640 in years 2–6 for versions listed over £40,000 | £200 |
| Reliability from real MOT tests | ||
| Reliability score | 120Well above average | 155Well above average (best) |
| Failed MOT first time (ages 3–20) | 25.5% | 20.9% (best) |
| Failed at 3 years old | 13.1% | 9.5% (best) |
| Failed at 5 years old | 13.8% | 11.2% (best) |
| Failed at 10 years old | 27.1% | 20.5% (best) |
| Most common MOT fault | Ball joint (4.5% of tests) | Tread depth (2.9% of tests) |
| Fails more than average on | Nothing stands out | Nothing stands out |
| MOT tests analysed | 362,136 | 122,625 |
| About the cars | ||
| Type | Executive car | Executive car |
| Owners' average miles a year | 8,900 | 11,000 |
| On sale | 2021 on | 2025 on |
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 A6 more reliable?
The Audi A6. Like for like on age and mileage, the Mercedes-Benz C-Class fails its MOT about 29% more often (reliability scores 155 and 120, where 100 is average). 20.9% of Audi A6s and 25.5% of Mercedes-Benz C-Classes failed first time in 2024.
›Which is bigger, the Mercedes-Benz C-Class or the Audi A6?
The Audi A6 is 226mm longer (4,999mm against 4,773mm). The Audi A6 has the bigger boot: 492 litres against 455.
›Which is cheaper to buy, the Mercedes-Benz C-Class or the Audi A6?
The Mercedes-Benz C-Class: new prices start at £46,995, £7,065 less than the Audi A6 (from £54,060). These are manufacturer list prices; dealers and brokers often sell for less.
›Which is cheaper to run, the Mercedes-Benz C-Class or the Audi A6?
Comparing petrol versions, the Audi A6 costs about £83 a year less to fuel at 7,500 miles (£1,450 against £1,533), using typical official economy and current UK average fuel prices.
›Which is safer, the Mercedes-Benz C-Class or the Audi A6?
Euro NCAP gave the Mercedes-Benz C-Class 5 stars (2022) and the Audi A6 5 stars (2024). 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 A6?
Pick the Mercedes-Benz C-Class for the lower price, or the Audi A6 for the bigger boot, the better MOT record and lower fuel costs. 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.