UK Motoring Glossary

Not a defect under the formal categories. The tester's note about a component approaching its limit, such as brake pads at 3mm.

The raised edge that forms at the outer rim of a brake disc as the friction surface wears. A lip taller than 1mm typically means replacement.

Hygroscopic hydraulic fluid (typically DOT 4 in modern cars). Should be changed every two years regardless of mileage.

New pad thickness is typically 10–12mm of friction material; replacement is usually advised at 3mm.

The MOT test class covering cars, light goods vehicles up to 3,000kg DGW, and most motor caravans — the test the majority of UK owners take.

A stolen or written-off vehicle wearing the identity (plates, V5C, VIN) of a legitimate vehicle of the same make and model.

Corrosion that weakens the vehicle within 30cm of a structural component — seat belt mountings, suspension mountings, steering box.

Payment in counterfeit Bank of England notes presented for high-value vehicles, often under time pressure at the seller's address.

MOT defect category for a fault that is a direct and immediate risk to road safety or the environment. The vehicle fails and must not be driven away.

Exhaust component that traps soot from a diesel engine. Removal or visible tampering is an automatic MOT fail.

Unique identifier stamped on the engine block. Recorded on the V5C; mismatches usually mean a replacement engine, not always fraud.

A fraudulent website posing as a marketplace's payment-holding service, used to steal payment for vehicles that do not exist.

Use of forged photo ID and a short-term rental address to take possession of hired vehicles, which are then disposed of abroad.

The vertical and horizontal alignment of the dipped beam. Measured at MOT against tolerances in the inspection manual.

Marker recorded against a vehicle's DVLA record when an insurer settles it as a total loss.

Re-registering a UK write-off in another jurisdiction (commonly Ireland) and bringing it back to the UK with a clean foreign identity.

MOT defect category for a fault that may affect the vehicle's safety or have an environmental impact. The vehicle fails the test.

Reducing the displayed mileage on the instrument cluster to misrepresent the vehicle's age and condition.

A drop or implausible gap in the recorded mileage between MOT tests. Visible free on the DVSA MOT history service.

MOT defect with no significant effect on safety or the environment. The vehicle passes, but the defect is recorded on the certificate.

Free DVSA service showing every MOT test result, mileage at test and recorded defects for a UK-registered vehicle since 2005.

Annual statutory roadworthiness inspection required for most UK vehicles over three years old, set by section 47 of the Road Traffic Act 1988.

The individual authorised by the DVSA to carry out MOT inspections at an approved test centre.

Standardised 16-pin diagnostic socket, mandatory on petrol cars sold in the EU/UK since 2001 and diesel since 2004.

An unsettled HP, PCP or lease agreement registered against the vehicle. The lender still owns the car until the agreement is paid.

Registration mark beginning with Q, issued to vehicles whose age or identity cannot be verified.

Measurement of the braking force at each wheel using rollers in the test bay floor. The primary method of brake testing in the MOT.

A worn shock absorber lets the car oscillate more than once after a firm push down on the corner. The MOT uses visual leak and play tests.

Any bulge, cut deep enough to reach the cords, or impact-related crack on a tyre sidewall is an immediate replacement.

Theft of a vehicle during an arranged test drive, using forged photo ID and proof of address to satisfy the seller's checks.

Inspection for free play in the outer steering joint, checked with the wheels jacked and a colleague rocking the road wheel.

UK legal minimum is 1.6mm across the central three-quarters of the tread, around the whole circumference, on all four tyres.

11-digit number on the top right of the V5C. Required for online tax, transfers and HPI-style checks.

A counterfeit or altered V5C used to support a cloned or stolen vehicle, or to pass a finance-encumbered vehicle as clear.

The DVLA-issued document showing the registered keeper of a UK vehicle. Not proof of ownership.

17-character unique identifier assigned to a vehicle at manufacture. Stamped on the chassis, etched into glass and stored in the ECU.

The vehicle's number plate, allocated by the DVLA and retained on the vehicle unless legally transferred.

Replacing or restamping the chassis VIN of one vehicle with that of another, usually to disguise a stolen car.

The first three characters of the VIN, identifying where the vehicle was built and by whom.