Automakers have been touting new diesel engines as much cleaner than your grandpa’s truck. But now the Volkswagen emissions scandal has regulators and consumers re-evaluating the technology. We took a look at the latest emissions data and found some surprises when it comes to “green” cars, including some powered totally by gasoline.
Earlier this month the U.S. Environmental Protection Agency (EPA) accused Volkswagen of installing software in its diesel engines that circumvented emission standards. The cars spewed up to 40 times more nitrogen oxides, a key component of smog, than allowed, according to the EPA.
To see how the latest diesels stack up against other fuel types, we looked at the EPA’s ratings at its fueleconomy.gov website. There, consumers select a state to begin their search for a vehicle. We chose California, since it is the biggest market and also has the most stringent air quality standards.
For the 2015 and 2016 model years, the top cars in terms of fuel efficiency and low smog emissions were, not surprisingly, electric vehicles. The BMW i3 BEV, Chevrolet Spark, Fiat 500e, Ford Focus Electric, and the Tesla Model S all scored 10 out of 10 on the EPA’s smog rankings.
No diesels made the top 50 list. Instead, a number of gasoline-powered hybrids, such as the Honda Accord hybrid, had good smog rankings, scoring 9 out of 10. Another popular car, the Honda Civic hybrid, earned a 9 or 7 smog score, depending on the engine configuration. The Toyota Prius earned a 9 for both the regular and plug-in hybrid models. Volkswagen’s Jetta gasoline hybrid earned a smog score of 9, although the EPA notes, in the wake of the scandal, that “updates may be made in the future” to the company’s ratings in the wake of the scandal.
A top-ranked all-gasoline car was the Honda CR-Z, with a smog score of 9 and a combined miles per gallon of 37. Gas-powered Honda Civics earned smog scores of 9 or 6, depending on the configuration. Ford’s Fiesta and Focus both earned a smog score of 6 and combined miles per gallon of 36 and 35, respectively.
“The cleanest way to go is to get a zero emission vehicle, a battery electric,” says Stanley Young of the California Air Resources Board. “Electric and plug-in cars are rapidly proving themselves, as not only cleaner but also cost- effective. It's hard to beat 108 miles per gallon [equivalent].”
But, he adds, “there are some very clean internal combustion gas engines now that meet our highest emissions standards.” Young suggests that consumers start their car search by browsing California’s smog data.
In another list, the American Council for an Energy-Efficient Economy didn’t include any so-called “clean diesels” in its greenest cars of 2015. At the top of the list were three electric cars, followed by the Prius C gas hybrid. The Prius plug-in hybrid also made the list, as did the Lexus CT 200H hybrid, the Civic hybrid (as well as its natural gas counterpart), and the Jetta hybrid.
The Volkswagen case already has changed the way diesel cars and light trucks will be tested in California. Last Friday, the state board announced that it will require more rigorous testing of the vehicles, including real-world driving tests and access to diagnostic data.