Hey Mr. Green,
I need to buy a new vehicle soon and am deciding between a 2010 Prius and the Volkswagen Jetta TDI Diesel Sedan, which just won Green Car Journal’s Green Car of the Year award. In your opinion, which car is better for the environment?
–Jonathan in Racine, Wisconsin
If you’re looking at the 2009 models, the Prius’s total carbon dioxide emissions are 4 tons per year, compared to 6.2 for a six-speed manual VW Jetta diesel according to the EPA. These numbers assume 15,000 miles per year, 45 percent in the city, 55 on the highway. The Prius also gets a better overall air-pollution score, because there are still some problems with diesel emissions, though the Volkswagen has made great strides in solving these.
Regarding 2010 models, the EPA has not yet listed ratings for the Jetta but puts the Prius at a combined city/highway rate 50 miles per gallon, and only 3.7 tons of carbon emissions. I hope the Jetta will come close to that. So keep an eye on the EPA ratings at this link for the latest comparison; the site also lets you recalibrate these basic numbers to your personal auto use. For example, the Prius gets better mileage in town than on the highway, whereas the Jetta does better on the highway. So if most of your driving is on the open road, the Jetta could be a better choice. To find out more about how green any vehicle is, look at the EPA’s information at this link.
Granted, there’s been a lot of buzz about the Jetta because one guy got more 58 mpg driving a Jetta around the country, and some others have beaten the EPA rating. But unless you’re one of these “hypermilers” whose driving practices are enormously prudent, you probably won’t match this.
OK, I already hear howls of protest from people who don’t trust the EPA ratings because their cars go a lot better or worse than EPA claims they should. There are even some conspiracy theorists convinced that the EPA is plotting with some car makers to bestow favorable or unfavorable ratings. But it’s more likely that the disparities result because the drivers of several hundred million cars in this country consist of both hyper- and hypo-milers. The hypos get rotten mileage mainly because they 1) drive too fast, 2) idle their engines excessively, and 3) neglect basic maintenance, like keeping tires properly inflated. All these can make a big difference in fuel consumption. Obviously, we should all strive to be hypermilers, and there are plenty of how-to-hyper ideas online.
My own experience suggests that bad driving explains much of the failure to match EPA ratings. I haven't owned a car in years, but I do rent them. The various vehicles I've driven over these years have usually equaled or exceeded the EPA’s ratings (when I prorate their performance to account for disgraceful speeding, they still meet the standard). Admittedly, this is not a controlled experiment, but it does suggest that the disparity between rating and reality lies not with the EPA, but with ourselves.