Euro Emission Standard Lookup

Euro emission standards explained

Euro standards are EU-derived regulations that set maximum limits on pollutant emissions from new vehicle engines — primarily NOx (nitrogen oxides), particulate matter, carbon monoxide and hydrocarbons. Each new standard tightens those limits. A vehicle's Euro standard is fixed at the point of type approval and does not change as the car ages.

The progression runs from Euro 1 (1992) through to Euro 6d (2020). Euro 3 vehicles are now well below modern limits. Euro 4 and Euro 5 cover most vehicles from the mid-2000s to mid-2010s. Euro 6 — the current standard — introduced much stricter NOx limits for diesels and has several sub-variants (6a through 6d) with increasingly rigorous real-world testing requirements.

Why Euro standard matters for UK fleet operators

The Euro standard directly determines where a vehicle can operate in the UK without incurring daily charges. London's ULEZ covers all 33 London boroughs and operates 24 hours a day. Petrol vehicles must meet Euro 4 (most petrol cars from 2006 onwards); diesel vehicles must meet Euro 6 (most diesel cars from September 2015 onwards). Non-compliant vehicles pay £12.50 per day.

Other UK Clean Air Zones — Birmingham's CAZ D, Bath's CAZ B, Bristol's CAZ C and others — use similar thresholds but apply them differently to cars, vans, taxis and HGVs. A vehicle that is ULEZ-compliant may still attract charges in a different zone depending on its class. For taxi and private hire fleets operating across multiple zones, keeping an accurate record of each vehicle's Euro standard is not optional.

The distinction between RDE2-compliant and non-RDE2 diesel also matters for company car tax. Non-RDE2 diesels carry a 4 percentage point BIK surcharge — meaning a driver in a non-RDE2 diesel pays more tax than one in an RDE2 equivalent, even if both are Euro 6. Most diesels type-approved from January 2021 are RDE2 compliant, but older stock in rental and taxi fleets often is not.