Buying a used car can be one of life’s most significant financial decisions, but new research shows that many second-hand vehicles on UK roads could be hiding serious secrets.

According to fresh data from diagnostics technology firm Carly, more than one in seven cars checked in the UK show signs of mileage rollback or vehicle identity manipulation.

This potentially leaves unsuspecting buyers out of pocket, facing costly repairs or even potential dangers.

Is it a bargain?

Based on over 2.5 million diagnostic scans carried out between January and September 2025, across 550,000 UK users, Carly found that 16.25% of vehicles had evidence of odometer tampering or VIN (Vehicle Identification Number) irregularities.

In practical terms, that means nearly one in every seven used cars may have been “clocked” (deliberately altered to display a lower mileage), or even misrepresented entirely.

Mileage fraud makes a car appear newer, more reliable, and more valuable than it truly is.

In reality, the vehicle could be far more worn, with hidden mechanical wear and a reduced lifespan.

This manipulation can inflate resale prices by thousands of pounds, misleading buyers and potentially creating safety risks.

Dali Ati, Head of Internationalisation at Carly, warned that the problem is both widespread and underestimated: “Mileage tampering can make a car appear newer and more valuable than it really is. But beneath the surface, it could be far more worn, and that’s where unexpected problems begin. We want drivers to feel informed and in control before they spend their money.”

Fraud Without Borders

Carly’s findings reveal that the problem is not confined to a single part of the country.

High-traffic regions such as London, Manchester, and Birmingham naturally see more fraudulent cases simply due to volume, but there is no significant regional difference overall.

Drivers in the North are just as likely to come across a clocked car as those in the South.

The issue arises amid a surge in used car demand, as economic pressures and soaring new car prices prompt more buyers to turn to second-hand options.

With the average new car now costing over £35,000, many motorists are seeking affordable alternatives.

Unfortunately, the rush to save money could put them at risk of buying vehicles with tampered histories.

How Carly Works

The Carly Used Car Check connects to a vehicle’s onboard diagnostics (OBD) port, scanning multiple electronic control units to verify whether the car’s mileage is consistent across all systems.

If discrepancies appear, for example, a lower reading on the dashboard than in the transmission or braking systems, the device can flag potential manipulation.

The check can also detect VIN mismatches and other data irregularities, providing a clearer picture of a vehicle’s authenticity before it is purchased.

As the used car market continues to grow, experts are urging buyers to stay vigilant.

A simple digital check could mean the difference between a bargain and a breakdown.