What are Euro 6 emissions standards? Why you need to know

The latest emissions standards - and why they could save you hundreds of pounds: all you need to know about Euro 6, and new Euro 6d cars

BuyaCar team
Mar 25, 2019

It's no longer enough to find your ideal car with the right colour, specification and optional equipment. Now, many diesel buyers need to check their vehicle's emission rating - and the key one to look for is Euro 6.

Euro 6 is the name given to a set of limits for harmful exhaust compounds. Since September 2015, manufacturers must ensure that new car emissions do not exceed those limits - as measured in an official test.

This standard has suddenly gained new importance because it will affect whether your diesel car will be charged to drive in new inner-city emission zones, being introduced this year - particularly if you have a diesel vehicle. 

These include London's ultra-low emission zone (ULEZ) and Birmingham's clean air zone (CAZ) More than 20 cities could implement similar policies.

Any diesel car or van that doesn't meet the Euro 6 requirements will be subject to a daily charge of up to £12.50 when driving in the city centres, in an effort to improve air quality. Rules for petrol vehicles are less strict because they have historically been cleaner.

So, in short, if you're buying a diesel car, a Euro 6-compliant model will ensure that you avoid clean air zone charges, under current rules. Petrol buyers don't need to worry about these fees unless their car is more than 12 years old.

That's not the whole story, though. New types of emission testing have generated even more jargon, including WLTP, RDE2 and Euro 6d. Some of these could affect the amount of car tax and company car tax that you pay. Read on for full details.


What are the Euro 6 emissions standards?

Current limits for harmful exhaust gases

Euro 6 emissions standards set the maximum limits for certain harmful gases and particulate matter a car is allowed to emit - chief amongst these are nitrogen oxides (NOx) and hydrocarbons. Petrol and diesel cars are subject to slightly different limits.

They replaced the previous set of limits - known as Euro 5, particularly tightening the restrictions on diesels. For a diesel to be Euro 6 compliant it cannot emit more than 80mg/km (0.08 grams per kilometre) of NOx gases, while a petrol can emit no more than 60mg/km.

Virtually every brand new car sold since September 2015 has had to meet the Euro 6 standard and many cars complied with Euro 6 early. However, the way that emissions are tested has changed to become more realistic. This has led to the latest Euro 6d standard.


Euro 6d diesel cars

Lower tax for the cleanest cars

At first, Euro 6 cars were tested for emissions and fuel economy only in a laboratory, on a rolling road. These tests were notoriously unrealistic when compared with real-world driving, where fuel economy was much worse and emissions higher.

The old test could also be manipulated - as illustrated by the dieselgate scandal, where Volkswagen was exposed as cheating. 

As a result, a new way of testing cars has been developed, involving mobile exhaust monitoring equipment (shown above), which measures emissions in real-world driving. From September this year, every type of new car must have gone through a road test to monitor emissions. The limits are higher than those in the laboratory test, and this standard is called Euro 6d-TEMP.

But from January 2022, new cars must pass the real-world test with lower limits, effectively equalling the levels in the laboratory test (with some allowance for the equipment). This stabndard is called Euro 6d and is expected to result in much cleaner new cars.

As a result, they will be cheaper to tax, particularly for business users, as Euro 6d diesel cars will not be subject to the 4% company car tax surcharge that applies to all other diesel cars. That could save a higher-rate taxpayer almost £500 a year for a £30,000 car.

Car tax in the first year will also be lower for Euro 6d diesel cars, as they won't be bumped up a car tax band, as other diesel cars currently are.

The first Euro 6d diesel cars have already gone on sale and include some versions of the following models:

  • Mercedes A-Class
  • Mercedes GLE
  • Jaguar XE
  • Jaguar XF

Click for the full list of cars

Petrol cars must also meet the same Euro 6d deadlines but there are no current benefits to buying a Euro 6d version, compared with one that complies with earlier standards.


What do RDE and RDE2 mean, and how do they impact Euro 6 cars?

Real-world testing procedure

RDE stands for Real Driving Emissions and is the on-road driving test that cars must undergo to ensure that they comply with Euro 6d-TEMP limits. RDE2 is the same procedure but with the stricter limits to comply with the Euro 6d standard.


What do NEDC and WLTP mean, and how do they impact Euro 6 cars?

Toughened-up lab tests

Car emissions continue to be measured in a laboratory, in addition to real-world testing, and this procedure has recently been tightened up.

Until recently, every car went through a cycle of accelerating, coasting and slowing down, called the New European Driving Cycle (NEDC). This originated in the 1970s and was designed for cars that were considerably less powerful and well-equipped than modern vehicles.

As such, it simply didn't reflect how cars are now driven, and produced unrealistically low emission measurements and high fuel economy figures.

In September 2017, it was replaced by the Worldwide harmonised Light vehicle Test Procedure (WLTP), which involves harder acceleration and more time at high speeds. This makes it tougher to pass, ensuring that car emissions really are clean and generating fuel economy figures that are more realistic.


Identifying a Euro 6 car

As Euro 6 became mandatory on all new cars from September 2015, many cars registered before that time – those on 2015 (15) registration plates and earlier – might only be Euro 5. However, as many cars met the standard early - such as the Mazda CX-5 that became so as far back as 2012.

So there are millions of cars that could comply with Euro 6. You'll find a car's emission standard in the technical information that accompanies many listings on BuyaCar. Be sure to ask for this to be double-checked to avoid the possibility of being hit with pollution charges in the future.


Benefits of a Euro 6 car

Emission-related charges

Motorists in London will soon (from 8 April 2019) have to pay to drive into the ULEZ (Ultra Low Emissions Zone) if they are behind the wheel of car deemed too polluting. For petrol cars, this means they must at least meet Euro 4 emission standards, but for diesels, they must at least meet Euro 6 standards.

It is expected that other major cities in Britain will follow suit with similar zones, so if you live in a city getting a cleaner car could well save you money every day. Read more


Company car tax

The benefits of buying a Euro 6 car depend on which sub-category you buy. Most don’t cut the mustard for those wanting to pay the least company car tax possible.

At the moment, diesel company cars automatically cost another 4 per cent in tax over a petrol with the same emissions, unless it's one of the few that meets the Euro 6d standard. For this reason, it makes sense to opt for cars which are at least Euro 6d compliant if you want to make the most savings, as well as the fact you are buying a more environmentally friendly car. Read more


Car tax (VED)

While individual car CO2 emission limits are not covered by Euro 6, compliant cars tend to have reduced CO2 emissions. Therefore, the better sub-category of Euro 6 a car meets, the more likely it is to have lower CO2 emissions, and the less it will cost you each year in VED (vehicle excise duty). That said, there is a VED levy for diesel cars which do not meet RDE2 standards. While the extra tax can cost under £20 for the year, it can also cost over £500 – so choose your car carefully. Read more


Euro emissions standards

Emissions standardDetailsEmission Zone and tax benefits
Euro 4Mandatory for all types of new car from January 2006Minimum standard for petrol cars to be exempt from London ULEZ and Birmingham CAZ
Euro 5All types of new car had to comply from January 2011
Euro 6New cars had to be Euro 6-compliant from September 2011Minimum standard for diesel cars to be exempt from ULEZ and CAZ
Euro 6d-TEMPNew cars must meet real-world testing limits from September 2019
Euro 6dTougher real-world testing limits are mandatory for new cars from January 2022Diesel cars exempt from company car and car tax surcharges

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