With rising fuel prices continuing to squeeze drivers’ finances, new data from automotive diagnostics specialist, Carly, brings further unwelcome news for motorists. An undercover investigation has found that drivers could be charged up to five-times the cost for a simple £110 sensor repair. Supporting the findings, a OnePoll survey of 2,000 UK-based motorists revealed that 52% either suspect or are unsure if they have been overcharged in the past five years, with many admitting they feel powerless when faced with repair bills.
To test the scale of the issue, Carly carried out a nationwide mystery shop to assess whether UK garages charge consistently for the same repair – and to gauge public confidence in the process. Using the same SEAT Ibiza with a known oxygen sensor fault, the investigation uncovered significant price disparities, with quotes reaching as much as £672, depending on the garage.
The mystery shop investigation, conducted by Carly across 10 UK garages spanning independent and main dealer networks, found that while every site correctly diagnosed the issue (P003100), many quoted significantly inflated prices. While the garages themselves are unable to be identified, Carly can say that a garage in Leeds (national chain) quoted £672 to replace both oxygen sensors, a main dealer in Stoke-on-Trent quoted £618 for oxygen sensor replacement and another main dealer, this time in Sunderland, quoted £328 for oxygen sensor replacement, all well over the £110 expected standard*.
Beyond inflated pricing, the investigation revealed a pattern of unnecessary upselling. Four of the ten garages recommended additional repairs or servicing that were unrelated to the known fault, including brake replacements, spark plugs, air-conditioning servicing, and duplicate diagnostics. In some cases, these add-ons would have added between £400 and £950 to the total bill, often without clear explanation of urgency, relevance, and immediate safety or drivability.
The mystery shop was complemented by a survey of 2,000 UK drivers conducted by OnePoll, which points to a wider concern – widespread confusion and distrust, with many unsure whether they have been overcharged in the past five years. Over half (56%) believe garages have the upper hand when it comes to repair costs, while 45% say they distrust garages or are unsure whether quotes are fair. Four in ten also say additional work is often recommended without a clear explanation.
Many drivers also report feeling underconfident when diagnosing car faults themselves. More than half of those surveyed (51%) say they are not confident identifying a serious problem before it becomes a breakdown, yet 69% say they would attempt to self-diagnose before visiting a garage. Perceptions of fairness vary across groups, with 62% believing women are more likely to be overcharged, while 53% feel drivers with limited car knowledge are at greatest risk.
Stuart Masson, Editorial Director at The Car Expert, said: “Rising fuel prices are putting extra strain on drivers’ finances, making it more important than ever to avoid unnecessary repair costs. Carly helps motorists identify, understand and solve issues early – keeping them in control of their maintenance spend.
“Carly’s investigation shows just how confusing and unpredictable car repairs can be. Even when every garage identified the same fault, quotes varied dramatically [some hundreds of pounds higher] and additional work was sometimes recommended unnecessarily. The real challenge for drivers isn’t just the cost, it’s the lack of clear information about what work is necessary and what a fair price should look like. Carly gives motorists the clarity and confidence to question quotes and make informed decisions before stepping into a garage.”
Commenting on the findings, Emma Brown, UK Growth Manager at Carly, added: “What this investigation highlights is a clear information gap between drivers and garages. Many motorists simply don’t have the tools to understand what’s wrong with their car or what a repair should realistically cost before agreeing to work. Carly is designed to close that gap; by identifying faults early, translating complex diagnostics into plain English, and giving drivers a clear idea of typical repair costs. It’s not about replacing mechanics, but about helping motorists walk into a garage informed, ask the right questions, and feel confident they’re paying a fair price.”
Carly’s smartphone app and scanner provides drivers with real-time manufacturer-level diagnostics, explanations of fault codes in plain English, and guidance on typical repair costs, helping motorists stay in control of their car’s health and costs.
The results of the investigation underline how unpredictable garage pricing can be for drivers, even when the issue is already known. With the cost of living still rising, unexpected repair bills can have a disproportionate impact, yet many motorists could reduce this risk simply by understanding what a fair repair should cost before visiting a garage.
Carly’s findings show how greater transparency in vehicle maintenance can translate into meaningful savings. By equipping drivers with clear fault information and typical repair costs in advance, Carly helps motorists question inflated quotes, avoid unnecessary work and approach repairs with greater confidence. Prices for Carly’s diagnostic solution start from £40.
