EPA updates procedures for determining mpg numbers of vehicles

Article by Andrew Christian, on February 26, 2015

The United States Environmental Protection Agency has issued updated procedures for determining fuel economy of vehicles – a challenging part for some carmakers in the last two years. EPA’s update covers how carmakers should calculate road load values in coast down tests, which gauges the rolling resistance and aerodynamic drag of a vehicle as it goes from 70 mph to a stop on a straight, flat track.

These values are usually used to program dynamometers that carmakers could use to calculate fuel economy ratings using the EPA’s test cycle. The update clarifies how carmakers should get vehicles ready for coast down testing and revises the test to monitor road load levels over a broader range of speed during the test.

According to Chris Grundler, director of the EPA’s Office of Transportation Air Quality, the updates will help ensure the fuel economy labels are accurate, and will help clarify how the agency expects the tests to be done.

EPA’s update comes after carmakers like Ford, Mercedes-Benz and Hyundai-Kia have had to rectify fuel economy labels on several models in the past two years due to coast down test errors, which prompted the agency to launch an to ensure the accuracy of mpg labels.

In November 2014, the South Korean carmaker settled a two-year EPA investigation, paying $350 million in fines – a result of exaggerated mpg labels on several Hyundai and Kia models in 2012 due to inaccurate road load values derived from coast down tests.

Ford also revised down the mpg ratings on a number of models in June 2014 after an internal audit of coast-down data uncovered errors in road load data derived from preproduction models. According to Grundler, the audits are continuing.

He said that the EPA has completed a round of coast down audits this year after auditing at least 70 models since 2012.

In the next months, the EPA will meet with carmakers to discuss their mpg testing operations, including about a loophole that enables them to apply the same fuel economy ratings to several nameplates sharing p owertrains and have similar weights.

Topics: epa, fuel economy

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