2018 What Car? Reliability Survey

More than 18,000 people told us about the reliability of their cars. Here we reveal the most - and least - dependable newer convertibles, coupes and sports cars...

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Claire Evans
30 November 2018

2018 What Car Reliability Survey

Convertibles, coupes and sports cars

Most reliable: BMW 2 Series coupe / cabrio - 97.0%

What went wrong? Exhaust 3%; Exterior lights 3%; Non-engine electrics 3%

Petrol-powered BMW 2 Series coupés and convertibles were by far the strongest performers in this category, with only 8% of cars suffering a fault. And although some cars were off the road for more than a week, all were fixed for free.

Our favourite convertible, the Mazda MX-5, is also the most reliable two-seater. Although 21% of cars had a fault, 10% related to the battery and were remedied in a day. There were also issues with the engine, gearbox/clutch and non-engine electrics. Some kept cars off the road for more than a week, but all were fixed under warranty.

Some 20% of Porsche 911s had a problem, but most (13%) were non-engine electrical issues that were rectified in a day. The 911’s overall score is dragged down by 7% of cars, which had engine problems that took more than a week to resolve. All cars were fixed for free, though.


2018 What Car Reliability Survey

Least reliable: Mercedes-Benz C-Class coupe / cabrio - 86.2%

What went wrong? Interior trim 17% Bodywork 6% Engine 6% Engine electrics 6% Non-engine electrics 6% Wheels/tyres 6%

The Mercedes-Benz C-Class Coupe and Cabriolet are proving nearly as unreliable as the saloon. The most common issues were with interior trim, followed by the engine and engine electrics. At least all cars remained driveable and were fixed for free.

Although the Audi TT sits in the bottom three, it did well to score a reliability rating of 90.4%. Most faults were minor, relating to interior trim (15%) and non-engine electrical systems (10%). Most cars were fixed in less than a week, but a few owners paid up to £500.

Again, although 40% of Porsche Caymans had a fault, the most common related to interior trim and non-engine electrics (both 13%), followed by bodywork, engine and gearbox/clutch (all 7%). Three-quarters were fixed in a day and all work was done under warranty.


Reliability for convertibles, coupes and sports cars aged one to four
Rank Make and model Score
1 BMW 2 Series coupe / convertible (2014-present) 97.0%
2 Mazda MX-5 (2015-present) 95.2%
3 Porsche 911 (2012-present) 94.5%
4 BMW M4 coupe (2014-present) 94.1%
5 BMW 4 Series coupe / convertible (2014-present) 93.5%
6 Ford Mustang (2015-present) 91.6%
7 Porsche Cayman (2013-2016) 91.0%
8 Audi TT coupe (2015-present) 90.4%
9 Mercedes-Benz C-Class coupe / cabriolet 89.1%

Reliability for convertibles, coupes and sports cars aged one to four


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