Paris experiences a pollution peak, March, 2015 | MARTIN BUREAU/AFP/Getty Images

The green car myth?

It’s not just diesel. Gasoline-powered cars also spew more pollutants than expected.

A new investigation showing higher-than-expected carbon dioxide emissions from gasoline-powered as well as diesel-powered cars is raising pressure on EU governments to examine whether a broader range of vehicles was also equipped with the cheating software that Volkswagen admitted to installing in its diesel vehicles.

The widening probe has the potential to cause serious trouble for the bloc's emissions reduction targets. About half the cars on European roads are diesel powered, and one of the sales pitches for those cars was that they were easier on carbon dioxide emissions than gasoline engines. With diesel in disrepute, that could mean shrinking sales that upends greenhouse gas reduction targets.

But it now appears that the real-world carbon dioxide emissions performance of new cars, including those that use gasoline, is significantly poorer than in highly artificial laboratory settings. That means both diesel and gasoline engines are worse for emissions than previously thought.

The difference in CO2 emissions during these tests can be as big as 40 percent depending on whether the car is examined in a lab or in the real world, where cars can burn through as much as 50 percent more fuel, the Brussels-based NGO Transport & Environment announced Monday as it called for a broader investigation.

Using legal techniques in the lab, such as optimizing engine controls or driving in higher gears, can cut CO2 emissions by as much as 40 to 45 percent, Greg Archer, the clean vehicles manager at T&E, said on a conference call. But for some new cars, including the Mercedes A, C and E class, BMW 5 series and Peugeot 308, that gap goes up to 50 percent.

“We’re at a loss to explain how these vehicles are achieving an even bigger gap,” Archer said.

There’s no proof the automakers used software to temporarily lower a car’s emissions during a test, the way Volkswagen did for nitrogen oxide emissions from its diesel cars, he added. “However, this data is very suspicious.”

“The European automobile industry’s success in reducing CO2 emissions has been, to a greater extent, dependent on higher sales of cars with diesel engines.”

The European Automobile Manufacturers’ Association (ACEA), countered that CO2 emissions from cars are measured in a test known as the New European Driving Cycle. And while its results, done in a lab, differ from those taken on the road, they still provide useful data.

“The purpose of the legal test is to enable a customer to make comparisons between vehicles in terms of their pollutant and CO2 emissions, based on a standardized test,” the association said Monday.

T&E, however, argues that the difference in what car buyers read in a car’s marketing material and what they pay at the pump adds up to around €450 per year in additional fuel costs.

As well as demanding a broader investigation into carbon dioxide emissions and fuel efficiency standards, T&E is pushing the European Commission to follow through with its plans to implement a new testing system, the Worldwide Light Vehicle Test Procedure, in 2017.

The Commission has met resistance from manufacturers and big car-making countries, including Germany, the U.K., France and Italy, said Archer, whose NGO has taken part in working group meetings.

The diesel problem

The news last week that Volkswagen rigged as many as 11 million diesel cars to cheat on emissions tests has also called into question the long-established belief in Europe that diesel-powered cars would help the Continent meet its greenhouse gas reduction goals. The company's reputation took a further battering on Monday, when its Audi luxury brand admitted to equipping 2.1 million of its cars with defeat devices.

“The Volkswagen case is embarrassing for the whole automotive industry in the current diesel debate,” said an auto industry lobbyist who requested anonymity. “It’s not welcome news.”

Diesel cars have long had problems with high emissions of nitrogen oxide, which is the main ingredient in smog. But the argument was that they did better on CO2, the principal greenhouse gas, as well as being more fuel-efficient.

Volkswagen appeared to have licked the problem by producing attractive diesel cars that also had low nitrogen oxide emissions — a breakthrough that has now been called into question.

UBS, the investment bank, said it expected that the closer scrutiny of diesel-powered cars will “accelerate the demise of the fuel in Europe,” at least for smaller cars.

Philippe Houchois, the author of the UBS report, said the Volkswagen scandal will lead to a renewed focus on EU emissions rules “where targets remain disconnected from real-life emissions and NOx compliance is proving challenging.”

The Volkswagen scandal is also likely to fuel calls to ban diesel from European cities and establish low-emission zones. “It’s not welcome news in the current debate,” the auto industry lobbyist said.

Road transport contributes about one-fifth of the EU’s total CO2 output, according to the European Commission, and is the only major sector in the EU where emissions are still rising.

“The policy focus within the EU over the past years has been on reducing greenhouse gas emissions,” said Erik Jonnaert, ACEA’s secretary general. “The European automobile industry’s success in reducing CO2 emissions has been, to a greater extent, dependent on higher sales of cars with diesel engines.”

The industry argument is that diesel vehicles help the EU achieve its mandated fleet average of emitting an average of 95 grams of carbon dioxide per kilometer. “Any limitation on diesel vehicles would have severe consequences for all manufacturers in being able to achieve that CO2 target,” Jonnaert said.

But industry watchdogs don’t buy the message that the fuel is key to reducing greenhouse emissions in Europe.

“The argument that diesel cars are a good solution to reduce CO2 emissions does not stand up. In Europe, diesel cars tend to be much bigger and more powerful with the result that they emit as much as petrol vehicles,” Archer said.

This article has been updated to clarify that higher carbon dioxide emissions apply to both diesel and gasoline-powered cars