Driver tools Car emissions - the worst offenders

• In our tests, 95% of diesel cars emitted more oxides of nitrogen (NOx) than limits allow
• One in ten petrol cars also defy NOx emission limits, in our tests
• Two thirds of petrol cars create more CO than allowed
• Emissions from some hybrid cars also exceed limits

Emissions - the worst offenders

In our tests, 95% of diesel cars, along with 10% of petrol cars, pump out more NOx than EU limits allow. The majority of petrol cars we've tested also exceed carbon monoxide (CO) limits - and some hybrid cars are not as innocent as claimed.

In light of the September 2015 Volkswagen Group emissions scandal, we extracted and analysed detailed emissions data for over 300 cars that we’ve tested since 2012.

What we found is that despite all of the vehicles officially complying with recent EU emission regulations, when you measure exhaust emissions in our more realistic tests, there is a chasm-like gap between the emission limits all cars should adhere to, and the large amount of emissions that cars actually pump out into our atmosphere.

What are the emission limits?

Every diesel and petrol engine (including hybrids) produces carbon dioxide (CO2), carbon monoxide (CO), oxides of nitrogen (NOx), hydrocarbons (HC) and particulate matter (PM) as exhaust emissions.

In January 1993, 'Euro 1' came into force, and specified limits that cars had to meet. In January 1997, Euro 2 replaced it with progressively tougher (lower) limits. In turn, this was superseded by Euro 3 in January 2001, Euro 4 by January 2006, Euro 5 in January 2011 and most recently Euro 6 in September 2015. (All dates refer to new car registrations).

Every car we've tested since 2012 officially complies with either Euro 5 or Euro 6, so they should be reasonably efficient. However, our tests are much more realistic than the official EU tests, and better represent the emissions that cars are actually discharging into our environment.

What we found is that most cars exceed official EU limits by pumping out more NOx or CO than Euro 5 or 6 limits allow - some by a very large margin.

Diesel NOx - the worst offenders

  • Worst offender emits 15 times legal NOx limit in our tests
  • The worst four cars would fail Euro 1 in our tests
  • Peugeot diesel-hybrid does not meet Euro 3

Only seven of the 153 diesel cars that we’ve tested since 2012 with official Euro 5 and Euro 6 engines actually produce less NOX than the limits allow. These are the worst, so far, from our tests:

Euro 5 limit - 0.18g/km
Euro 6 limit - 0.08g/km

Jeep Grand Cherokee, 3.0-litre (2011-) - emits 2.7 g/km of NOx.
By far, the biggest NOx creator in our table. Shovels 15 times the amount of NOx into the atmosphere than its Euro 5 engine is allowed to.

Subaru Forester, 2.0-litre (2013-) - emits 1.19 g/km of NOx
Its Euro 5 engine pumps out more than six and a half times as much NOx as its engine should let.

Nissan X-Trail, 1.6-litre (2014-) - 1.05 g/km of NOx
The Nissan X-Trail is the only official Euro 6 engine we’ve tested that fails to meet even Euro 1 standards from 1993. In our tests, it emitted 13 times as much NOx as the Euro 6 limit.

Nissan Qashqai, 1.6-litre (2014-) - emits 0.99 g/km of NOx
A top selling car, it chugs out so much NOx that it also wouldn’t meet Euro 1 standards.

KIA Sportage, 2.0-litre (2010-) - emits 0.93 g/km of NOx
The four-wheel drive version of this Kia only just meets Euro 1 criteria. That's ok - if you happen to do your driving in 1993.

Hyundai Santa Fe, 2.2-litre (2012-) - emits 0.9 g/km of NOx
Look beyond the exotic name, and the bonnet, and you'll find a Euro 5 engine that chucks out large amounts of NOx.

Land Rover Range Rover Sport, 3.0-litre (2005-2013) - emits 0.87 g/km of NOx
This Range Rover produces nearly five times the Euro 5 allowed amount of NOx.

Volvo S60, 2.0-litre (2010-) - emits 0.84 g/km of NOx
This car has a Euro 6 engine, but manages to emit ten times more NOx than the limit.

Volvo XC90 2.4-litre (2002-2015) - emits 0.84 g/km of NOx
Volvo’s big 4x4 may have a luxurious interior, but like all cars in this top ten, it’s a NOx factory on wheels.

Highest NOx emitting diesel-hybrid:

Peugeot 508 RXH, diesel-electric hybrid (2012-) - 0.53 g/km
Though not in the top ten, this Peugeot is worth mentioning as, though it’s a hybrid, it still pushes out three times the Euro 5 NOx legal limit.

Petrol NOx - the worst offenders

  • The three worst petrol cars listed here produce so much NOx, they would fail the Euro 3 standards.

Petrol engines produce NOX – most in such small quantities that it’s not of consequence. But our tests reveal that 10% of petrol cars exceed NOX limits. These are the five worst:

Euro 5 and Euro 6 limit - 0.06g/km

Mercedes-Benz SL, 3.5-litre (2012-) - emits 0.2 g/km of NOx
This sporty car from Mercedes creates three times as much NOx as petrol limits allow. To put that in perspective, it’s the only petrol car we've seen that would also fail diesel equivalent Euro 5 limits.

Mercedes-Benz E-Class, 2.0-litre (2009-) - emits 0.17 g/km of NOx
In terms of cars that produce the most amount of NOx from its petrol engines, Mercedes also takes the second spot. The E-Class is almost as bad as the SL, despite the fact it has what should be a cleaner Euro 6 engine.

Mini Cooper, 1.5-litre (2014-) - emits 0.16 g/km of NOx
It might be fun to drive, but its Euro 6 engine pushes out nearly three times the amount of NOx as it’s supposed to.

Nissan Pulsar, 1.2-litre (2014-) - emits 0.15 g/km of NOx
The small-family sized hatchback may not be the biggest car about, but it creates a big stink in our tests. It only, just, complies with Euro 3 emission levels.

Nissan Qashqai, 1.2-litre (2014-) - emits 0.12 g/km of NOx
Just like the diesel version, the petrol version of the Qashqai also exceeds NOx limits. It's not as bad as the diesel, but it's still the fifth highest creator of NOx of all petrol cars we've tested so far.

Petrol CO - the worst offenders

  • The Nissan Note and Toyota Aygo might be small, low powered cars – but they produce more CO than a Porsche 911.

Invisible and odourless, carbon monoxide (CO) is a potentially harmful gas. Diesel cars don't really produce much CO - it's petrol cars that our tests have revealed to be the problem:

Euro 5 and Euro 6 limit - 1 g/km

Hyundai Veloster, 1.6-litre (2012-2014) emits 6.11 g/km of CO
Top of the CO charts, the Veloster produces six times as much CO than the limit.

Nissan Note, 1.2-litre (2013-) emits 5.36 g/km of CO
The 1.2 engine may sound small but it’s big enough to produce over 5.3 g/km of CO – over five times the limit.

Toyota Aygo, 1.0-litre (2014-) emits 4.91 g/km of CO
Another supermini that pushes out a massive amount of CO.

Alfa Romeo Giulietta, 1.4-litre (2010-) emits 4.69 g/km of CO
Romeo, Romeo, quite a gassy Romeo. Produces four and a half times the legal limit of CO.

Nissan 370Z, 3.7-litre (2009-) emits 4.63 g/km of CO
This sporty number creates nearly as much CO as the Giulietta, above.

Hyundai i20, 1.2-litre (2009-2014) - emits 4.61 g/km of CO
Another supermini sized car, it too creates 4.5 times as much CO as it should.

BMW 4-series, 2.0-litre (2014-) emits 4.53 g/km of CO
A convertible, the 242bhp engine also creates 4.5 times the legal limit of CO.

BMW 2-series convertible, 2.0-litre (2014-) emits 4.33 g/km of CO
The 2-series creates a near identical amount of CO as the larger 4-Series.

Porsche 911 Carrera, 3.8-litre (2011-) emits 4.2 g/km of CO
The 911 produces four times the legal amount of CO.

Hyundai i10, 1.0-litre (2014-) emits 4.09 g/km of CO
A 1.0 litre city car it may be, but it creates just as much CO as the Porsche.

Lexus LS, petrol-electric hybrid (2013-) emits 3.95 g/km of CO
11th in the table, it's worth mentioning this Lexus as it's a petrol-hybrid that generates four times the legal amount of CO.

Best Buys removed

We’ve found that of the cars we’ve tested, 85 exceed Euro 3 limits (passed 2001) in our tests. This means these 85 cars do not pass the earliest emission regulations from this century.

Five of which had previously performed well in enough in areas like performance and ride comfort to be named as Best Buys – but in light of our findings, we have now removed Best Buy awards from these cars.

We have also removed Best Buy awards from 23 Volkswagen Group cars following the dieselgate scandal.

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