Data from Warranty Solutions Group (WSG) has found that the Mercedes-Benz E-Class is the least reliable used convertible.
WSG analysed one year of warranty claims, with the E-Class convertible returning a claim rate of 27.97%, with suspension problems and roof mechanism issues contributing to this.
The current generation MK4 Mazda MX-5 was ranked as the most reliable convertible, with its low claim rate of 7.69% attributed to its simple engineering, reliable engines, and robust manual gearboxes.
Martin Binnee, operations director at WSG, said: “As convertible ownership continues to grow in the UK, this ranking offers a valuable guide for both dealers and consumers – highlighting models that won’t just turn heads, but also go the distance.
“The Mazda MX-5 remains a standout example – its long-standing reputation for durability continues to be validated by What Car?, J.D. Power, and Consumer Reports.
“It consistently outperforms expectations, reinforcing the value of engineering simplicity and mechanical integrity in an era of increasing complexity.”
Premium cars also performed well, with the BMW Z4 produced since 2019 (G29), achieving second (9.20% claim rate), which WSG attributed to its modern architecture and Toyota’s involvement in the development process.
The Porsche Boxster placed third, with a claim rate of 11.67%, with WSG praising the current 982 generation’s turbocharged flat-four engines for their refinement, while praising previous generations for the durability of their naturally-aspirated flat-sixes.
The Boxster was also praised for its ‘world-class’ build quality, and the low mechanical strain provided by the even weight distribution provided by its mid-engined layout.
Binnee said: “Historically, the Achilles heel of convertibles has been their susceptibility to faults such as Nox sensor failures, battery drain, and thermostat issues, symptomatic of the wider challenges around electronics integration and environmental exposure.
“Electrical faults, in particular, have emerged as a persistent pain point for owners.
“Yet the tide is turning. Brands like MINI, BMW, and Audi have made significant strides, closing the reliability gap with enhanced quality control, better system integration, and platform maturity.
The data covered 3,000 extended warranty claims from the last year, including only models with at least 100 warranty sales.
Binnee said: “Ultimately, consumers are demanding more than just style – they want confidence. And in today’s market, reliability is fast becoming a key pillar of brand trust and long-term value.”
