Buying guide · 7 min read

ULEZ and Clean Air Zones: will your next used car be charged?

If you live in or drive into London or a city with a Clean Air Zone, buying the wrong used car can cost you a daily charge every time you drive. The rules are simple once you know the Euro standard you need, and checking takes a minute.

Written by the VehicleFaults Research Team · reviewed October 2026

1. The basic rule

London's Ultra Low Emission Zone and most English Clean Air Zones that charge private cars use the same standards.

Petrol cars need to meet Euro 4, generally cars first registered from 2006, many from 2001
Diesel cars need to meet Euro 6, generally cars first registered from September 2015
Fully electric cars are compliant
Hybrids follow the rule for their engine type, petrol or diesel

2. How to check a specific car

Use Transport for London's vehicle checker for ULEZ, it takes the registration
Use the GOV.UK Clean Air Zone checker for other cities
Do not rely only on the registration date, some cars registered close to the cut-off do not comply
Ask the seller for the Certificate of Conformity if the checker is unsure

3. Emissions faults that matter on Euro 6 diesels

A compliant diesel still needs its emissions equipment working, both for the MOT and to avoid big bills.

DPF warning lights or frequent regeneration on short-trip cars
AdBlue warnings or a no-restart countdown on the dash
EGR valve faults causing limp mode or flat spots
Signs the DPF has been removed or tampered with, which is illegal and an MOT failure

4. Who should still buy a diesel

If you mostly do long motorway journeys, a Euro 6 diesel can still make sense. If most of your driving is short town trips, a petrol, hybrid or electric car avoids most DPF and AdBlue problems.

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Frequently asked questions

Is my 2014 diesel ULEZ compliant?

Most diesels registered before September 2015 are not Euro 6 and would be charged. Check the exact car on the official checker, as a few earlier cars do comply.