The topic of tailpipe emissions, be they actual pollutants, or carbon dioxide, is never far from the headlines.

For the typical everyday motorist, it influences not just your car tax rates but also where you can go. Clean Air Zones within British cities dictate whether, or not, you need to pay extra taxes to enter and this depends on the emissions standards that your car model was certificated as meeting by the European authorities, when it was new.

What are Euro Emissions standards?

According to the Society of Motor Manufacturers and Traders (SMMT), the mandated Euro Emissions Standards have been responsible for slashing new vehicle hydrocarbon emissions in half, NOx by 84% and particulate matter by 96%. That was back in 2017 and so the contributions that this legislation has made to air quality are likely to have increased.

How can you find out your vehicle’s Euro standard?

Not all cars have the Euro emissions standard printed on a sticker on the inside of a front door jamb - in which case, you will find your car's compliance standard listed on the V5C vehicle registration document. Online checks are feasible, too, using the UK government web link: https://www.gov.uk/get-vehicle-information-from-dvla.

Your motorcar would not have been tested but a representative example would have been, for the manufacturer to sell that model range legally in the UK and EU. The lists below provide an overview of when the legislation appeared for new passenger

cars and an approximate introduction date. You may find the Euro number displayed as Roman numerals but the reference is the same:

Euro 1 (1993):

While emissions legislation pre-dated the first Euro standard, Euro 1 kick-started consistent, regular and ever-tightening regulations. Euro 1's introduction mandated that new cars had to be fitted with catalytic converters and use unleaded petrol.

The prime aims were to reduce hydrocarbons (HC), carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx). Only diesels had to meet particulate (PM) standards.

The prescribed Euro 1 limits for motorcars were:

CO – 2.72 grammes per kilometre (g/km)

HC+ NOx – 0.97 g/km

PM – 0.14 g/km (diesel only)

Euro 2 (1996):

This updated standard built upon the basic blocks, established by Euro 1. It cut the CO, HC and NOx limits and commenced different limits for petrol and diesels. By this time, many diesels were also fitted with oxidising catalytic converters. The limits were:

CO – 2.2 g/km (petrol), 1.0 g/km (diesel)

HC+ NOx – 0.5 g/km (petrol), 0.7 g/km (diesel)

PM – 0.08 g/km (diesel)

Euro 3 (2000):

Euro 3 saw the CO and diesel particulate limits reduced further. Diesels were also required to meet NOx targets, although these were still three times higher than the petrol limits.

CO – 2.3 g/km (petrol), 0.64 g/km (diesel)

HC – 0.20 g/km, 0.56 g/km (diesel)

NOx - 0.15 (petrol), 0.50 g/km (diesel)

PM – 0.05 g/km (diesel only)

Euro 4 (2005):

In the mid-noughties, Euro 4 saw these limits cut again for petrol and diesel, although petrol engine particulates continued to be unregulated. The limits were set as:

CO – 1.0 g/km (petrol) 0.50 g/km (diesel)

HC – 0.10 g/km (petrol), 0.30 g/km (diesel)

NOx – 0.08 (petrol), 0.25 g/km (diesel)

PM – 0.025 g/km (diesel)

Euro 5 (2010):

Euro 5 focussed more on particulate output. While direct-injection petrol engines were good at reducing CO2, they produced higher levels of cancer-causing particulates. Therefore particulate levels were reduced, especially for diesels, where particulate filters (DPFs) had to be fitted to comply.

CO – 1.0 g/km (petrol), 0.50 g/km (diesel)

HC - 0.10 g/km (petrol), 0.23 g/km (diesel)

NOx – 0.06 g/km (petrol), 0.18 g/km (diesel)

PM – 0.005 g/km (direct injection petrol and diesel)

Euro 6 (2014):

The main focus of Euro 6 was to tighten diesel NOx emissions. This led to many manufacturers fitting NOx traps, or NOx catalysts (SCR, or Selective Catalytic Reduction), the former of which requires a urea-based emissions fluid (sold under the trade name, AdBlue). Interestingly, particulate levels remained the same for both petrol and diesel vehicles, as the limits below show:

CO – 1.0 g/km (petrol), CO – 0.50 g/km (diesel)

HC – 0.10 g/km (petrol), 0.17 g/km (diesel)

NOx – 0.06 g/km (petrol), 0.08 g/km (diesel)

PM – 0.005 g/km (direct injection petrol and diesel)

Euro 6b/6c/6d/6e (2017):

After the emissions cheating scandal, legislators realised that the laboratory tests were not representative of real-world conditions and could be manipulated. Therefore, a stricter Worldwide Harmonised Light Duty Test Procedure (WLTP) was introduced along with a Real Driving Emissions (RDE) on-road test.

This took some time and the test methods evolved, so some cars may be registered as being Euro 6b, or Euro 6c.

You may find cars registered before 2020 as being Euro 6d-temp compliant. This means they passed the emission limits standard requirements during the early implementation stage of Euro 6d, which had slightly less strict NOx limits to help manufacturers. Later compliant cars are classed under Euro 6d.

Overall, the emissions limits remained the same for Euro 6; it was the testing methods that evolved.

That was until the introduction of ISC - In-Service Conformity Tests - in 2019. This had to ensure that cars aged five years, or having covered 62,000 miles had to go through a formal type-approval emissions test. A new test that assessed petrol evaporation emissions (EVAP) came in from September 2019, which caused carmakers even more headaches.

For the first time, Euro 6e-bis (from 2025) focussed on carbon dioxide (CO2) emissions and made the testing regime longer for Plug-In Hybrid Electric Vehicles (PHEVs). This means that PHEVs, tested under Euro 6e-bis, will be rated with higher CO2 emissions, compared with Euro 6d.

The UK's HMRC had signalled its intent to use Euro 6e-bis CO2 test values for Benefit in Kind (BIK) tax from 2026 but, at the time of writing, appears to have backtracked and reports indicate that the government will use the lower Euro 6d limits for tax purposes, where applicable. It is reported that stricter still "Euro 6e-bis FCM" tests will follow in 2027, which will push up official PHEV CO2 ratings even higher.

Euro 7 (2025):

The introduction of Euro 7 has been subject to much industry pushback for being too strict. At the time of writing (April 2025) latest introduction date is mooted for July 2025.

Broadly, the tailpipe standards for Euro 7 remain the same as per Euro 6, albeit with a reduction in PM from 0.005 g/km to 0.0045 g/km for both petrol and diesel engines.

A major difference is that Euro 7 shall examine other emissions aside from those from the tailpipe. These include particles shed from tyres and dust from brake friction parts. High voltage cars will also not escape entirely, because the standard will also assess battery durability.

Testing methods will also be stricter and ISC limits will be extended from 5 years / 62,000 miles to 10 years/125,000 miles.

Penalties for non-compliance with EU emission standards

As it is the carmakers that must comply with EU Type Approval emissions standards, car owners need not be concerned about being exposed to heavy penalties for non-compliance.

However, if you plan to modify your car, be aware of falling foul of the Road Vehicles (Construction and Use) Regulations (Regulations 61(7) and 61A(3)) and the Road Traffic Act 1988 (Section 42), which state that you commit an offence if you use a vehicle on a road a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet.

Does my car’s Euro standard affect my MOT?

The MOT test does not enforce European Type Approval emissions standards directly. The MOT Test has different limits for its exhaust emissions tests, according to the age of the vehicle presented, and dependent on the Euro Emissions standards.

In light of diesel-gate, where mainly Euro 5 diesels did not meet their Type Approval exhaust emission limits outside of laboratory testing, MOT emissions testing was made stricter for certain ages of car. These changes occurred in 2018 and included visual checks for missing diesel particulate filters on Euro 5 and 6 vehicles.

How does my car's Euro Standards affect tax?

The UK government has used emissions test results as a means of setting not just Vehicle Excise Duty (VED or 'car tax') but also company car tax and Benefit-in-Kind rates.

Euro Emissions standards are of particular relevance, when entering built-up areas with Clean Air Zones, where non-compliant vehicles will pay a fee. More information on this topic can be found at: https://www.gov.uk/clean-air-zones.

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