July was the Greenest Month Ever for U.S. Car Sales

Thanks to product innovation and good old-fashioned engineering, America’s gas-guzzlers are slimming down.

08.06.13 9:25 PM ET

July proved to the greenest month ever for the American car industry—again. Every month, the University of Michigan Transportation Research Institute tallies up the fuel efficiency of vehicles sold and then comes up with a measure for the average mileage of the new fleet that hit the road. In July, it was 24.8 miles per gallon. That level, the highest since UMTRI began tallying it several years ago, has been reached four times so far this year.

There are some obvious reasons for the greening of the car fleet. Hybrid, plug-ins and clean diesel car sales have been on the rise as car owners hoping to avoid the pump search for more energy efficient, high mileage vehicles. According to the helpful monthly dashboard published by, the number of hybrids sold in July—45,494—was the highest sold since July 2009.

Although the hybrid has traditionally been the green car of choice, plug-ins and diesel vehicles have are on the rise as other pump-friendly alternatives. Volkswagen’s Jetta and Passat diesel cars did very well in July—with sales increasing by 27.3 percent and 17.4 percent respectively when compared to June. Encouraged by this success, Audi, Grand Cherokee and Ram all have plans to launch diesel vehicles going forward. In June Volkswagen set out to break the record for best mileage by driving across the country in the Passat TDI Clean Diesel passenger car. 48 states and 8,122 miles later the Passat earned a Guinness World Record for the lowest fuel consumption for a non-hybrid car. The VW Passat TDI, which is run on ultra-low-sulfur diesel, averaged 77.99 MPG for the entire trip, smashing the previous record of 67.9 MPG.

Plug-in cars like Chevrolet’s Volt, Tesla’s Model S, and Nissan’s Leaf, account for only a tiny sliver of sales. But the real gains in the fleet’s mileage aren’t coming from futuristic vehicles that use no gas. They’re coming from substantial, continuous improvement to conventional cars. Thanks to engineering advances, SUVs, coupes, sedans, and sports of all makes get substantially better mileage today than they did last year, or just a few years ago. The 2014 Jeep Cherokee, for example, can get up to 30 miles per gallon on the highway.

The upshot is that, with each passing month, Americans effectively use less petroleum to get around. The University of Michigan Eco-Driving Index (EDI), which estimates the monthly greenhouse gases emissions generated by individual drivers, proves that American drivers are becoming more aware of and careful about the impact their cars have on the air we breathe. The most recent figures show the EDI at 0.81 (the lower the number the better) in May 2013, down from .83 in May 2012. These numbers represent an overall improvement of 19 percent since October 2007. And any improvement is welcome—U.S. highway vehicles now let off more the 1.5 billion tons of greenhouse gas emissions annually.