What Are the Most Polluting Cars?

A new survey conducted by Which? online comparison site has found that Jeep, Renault, Nissan and Ford are among the most polluting cars on the road. The site tested 26 different brands of the most popular diesel automobiles on the market and found that while all of them complied with the Euro Standards Emissions regulations, the amount of nitrogen oxides (NOx) that each emitted varied greatly.

Real conditions, real results

The Which? survey took in a variety of different cars from a multitude of brands, testing both those which complied with the 2009 Euro 5 Standards and the more recent (and supposedly more stringent) Euro 6 Standards, brought in in 2005.

Despite the introduction of the new regulations, it has become clear that the tests themselves are unreliable as they do not simulate real-life driving conditions. For example, manufacturers are allowed to enter vehicles with air conditioning switched off, tyres overinflated and economy-mode switched on, all of which work to distort the results.

What’s more, the tests do not put excessive strain on the vehicle in terms of acceleration or speed – something which many drivers do. As a result, it was recently found that as much as 90% of new diesel cars in Europe emit illegal levels of pollution. Which? addressed this discrepancy by making their test conditions more reflective of the real world.

Top of the class

BMW, Mini (who are owned by BMW) and Toyota were found to produce the least amounts of NOx in all of the vehicles that were tested. BMW and Toyota both showed impressive improvement in the level of emissions between cars that complied with the Euro 5 and Euro 6 Standards.

Elsewhere, the Volkswagen family of cars (VW, Seat, Audi and Skoda) all performed surprisingly well, delivering some of the lowest emissions results. However, in the wake of the VW scandal in 2015, in which it was proven that VW were installing “defeat devices” on their vehicles in order to purposely manipulate test results, fears remain that their performance in the Which? tests may also be untrustworthy.

Volvo also produced comparatively little amounts of NOx, though discouragingly, their newer series of cars actually emitted more pollutants than their previous range.

Bottom of the pile

At the other end of the scale, the 16 Renault cars tested by Which? had the poorest results of any brand. In fact, even those models which reportedly comply with the Euro 6 Standards emitted more emissions than most cars from other brands which only met Euro 5 Standards.

The fact that Renault and Nissan share a strategic partnership and work together to develop engines mean that it comes as little surprise that Nissan were the second most polluting brand tested. Meanwhile, the two Jeep cars in the survey produced the most alarming amounts of NOx, with both of them emitting almost 10 times the legal limit under the Euro 5 regulations.

Ford, who make two of the top ten selling diesel models, also performed badly, with the 12 cars tested performing well below average.