Source: UCS. Click to enlarge.

Stronger tailpipe emissions standards have led to an 87% reduction in smog-forming tailpipe emissions from the average car or truck since 2000, while global warming emissions from the average vehicle have decreased by nearly 20% percent since 1998.

Despite this progress, UCS noted, Ford, General Motors, and Chrysler still have higher than average new fleet smog-forming and GHG emissions.

Using the adjusted, most up-to-date information on Hyundai-Kia’s vehicles after the automaker had to revise its performance data with the US EPA, the findings show that the automaker came out in first place thanks to a concerted effort to improve the green performance of its fleet by turbocharging and downsizing engines in a number of its models while also introducing hybrid-electric versions of two of its top-selling vehicles, the Hyundai Sonata and Kia Optima.

This report marks the first time another company has bested Honda, which came in second this year but has earned every “Greenest Automaker” designation from UCS since 1998.

Honda continues to lead the way in many vehicle classes, but it has started to lag the industry average in its midsize fleet—which includes its best-selling Accord, and accounts for a quarter of the company’s sales.

—Dave Cooke, vehicles analyst in the UCS Clean Vehicles Program and author of the report

Ford led the Detroit automakers while achieving the greatest percent reduction in smog-forming emissions of any manufacturer evaluated. The company also showed strong improvements in GHG emissions due to its increased use of hybrids and its focus on smaller, turbocharged engines in vehicles ranging from the Ford Focus sedan to the F-150.

Automakers are employing a number of different technologies to reduce global warming emissions from their vehicles. Percentages indicate the fraction of MY2013 vehicles sold with the given technology. The gray segments represent models sold by smaller automakers, which are not ranked in the report. Source: UCS. Click to enlarge.

Methodology. To develop the ranking, UCS averaged the per-mile emissions for each light-duty vehicle sold by each automaker.

To determine GHG emissions, UCS considered the fuel economy, fuel type, and sales volume of each type of vehicle sold by each automaker in the 2013 model year (MY2013). UCS also considered the upstream global warming emissions from producing and distributing the fuel used by each vehicle, as well as emissions from the vehicles themselves.

UCS then calculated the sales-weighted average global warming emissions for each automaker—as well as for all eight together. UCS assigned the industry average a score of 100, and then give each automaker a score indexed to the industry average.

To calculate smog-forming emissions for each vehicle, UCS similarly considered tailpipe emissions of NO_x and non-methane organic gases (NMOG, a measure of VOC), as well as those emissions during the production and distribution of the fuel used by the vehicle. UCS again assigned a score of 100 to the industry average, and index each automaker’s results to that average.