WASHINGTON—The U.S. Environmental Protection Association issued on Feb. 23 updated procedures for a critical part of fuel economy testing that some auto makers have struggled with in the last two years.
The update covers how auto makers should calculate road load values in coast down tests, which measure the rolling resistance and aerodynamic drag of vehicles as they glide from 70 mph to a stop on a straight, flat track. Those values are used to program dynamometers the auto makers use to calculate fuel economy ratings using the EPA's test cycle.
The update clarifies how auto makers should prep vehicles for coast down testing and updates the test to monitor road load levels over a broader range of speed during the test. Chris Grundler, director of the EPA's Office of Transportation Air Quality, said the changes will help ensure the accuracy of fuel economy labels, and clarify how the EPA expects the tests to be done.
“It will be more accurate,” Grundler said. “Both the EPA and the auto makers have a common cause to make sure that customers are getting the best information.”
The update comes after Ford Motor Co., Mercedes-Benz and Hyundai-Kia have had to correct fuel economy labels on several models over the last two years due to errors made on the coast down test. The errors prompted a beefed-up audit initiative by the agency to ensure the accuracy of mpg labels.
In November, Hyundai and Kia agreed to settle a two-year EPA investigation and pay a $350 million fine after fuel economy labels on several Hyundai and Kia models were found to be exaggerated in 2012 due to inaccurate road load values derived from coast down tests.
Ford cut the mpg ratings on several models in June after an internal audit of coast-down data using production vehicles uncovered errors in road load data that were based on preproduction models.
The Hyundai-Kia incident prompted the agency to resume coast down audits for the first time in decades, and Grundler said the audits are continuing. The agency completed a round of coast down audits this year after auditing at least 70 models since 2012.
“I think it's fair to say that not only are we paying more attention to these processes but the auto makers are as well, and that obviously is welcomed,” he said.
In the next few months, the EPA will meet with auto makers to discuss their mpg testing operations, Grundler said. Among the issues that the EPA plans to discuss is a loophole that allows auto makers to apply the same fuel economy ratings to multiple nameplates that share powertrains and have similar weights. The practice tripped up Ford when it had to sharply lower the C-Max's mpg label in August 2013.
Grundler said the agency hasn't closed the loophole yet but wants to make sure that fuel economy labels closely reflect real-world performance.
“We still are very concerned about how auto makers are grouping these vehicles,” he said. “We think that these groupings are narrowing but we want to have more confidence on that.”