In the wake of multiple incidents of misstated window-sticker ratings, government regulators are reevaluating how carmakers test for fuel economy.

The U.S. Environmental Protection Agency (EPA) said Monday it will issue new guidelines for fuel-economy testing.

MORE: EPA To Tighten Gas-Mileage Test Rules, Audit More Ratings From Carmakers

Last year, the EPA said it would issue new formal regulations--but has decided to go with these non-binding guidelines instead, according to The Detroit News.

Among other things, the new guidelines detail how vehicles should be prepared for testing--including the acceptable amount of tire wear and specifics on how they should be broken in.

2013 Lincoln MKZ Hybrid

2013 Lincoln MKZ Hybrid

The guidelines will also address "road load"  or "coast down" tests, which are used to measure aerodynamic drag and tire rolling resistance.

The results of these tests are used to program a chassis dynamometer, which is used for actual fuel-economy testing while the car is stationary.

Currently, the test is conducted while cars coast down from 70 mph on a straight, flat test track, but the new guidelines call for it to be done at 50 mph.

RELATED: EPA Wants Carmakers To Verify Gas Mileage With Road Testing Too

The agency said it will issue its guidelines in lieu of new rules to save time. It typically takes two to three years for the EPA to draft a legally-binding rule.

It will use the new guidelines when it conducts audits of automakers.

Agency officials had also previously discussed closing a loophole that allows manufacturers to assign the same fuel-economy ratings to vehicles in the same weight class with identical powertrains--as Ford initially did with the C-Max Hybrid and Fusion Hybrid.

2012 Kia Soul

2012 Kia Soul

This negates any effect of differing drag coefficients on the fuel economy of those vehicles, but according to the story, the EPA may back away from this proposal.

In August 2013, Ford had to slash the gas-mileage ratings for the C-Max Hybrid and compensate owners for the discrepancy.

The Dearborn carmaker then had to cut them a second time in June 2014--along with those of five other models.

ALSO SEE: Hyundai, Kia To Pay $300 Million For Gas-Mileage Testing Errors

Meanwhile, Hyundai and Kia paid $300 million in penalties last year after misstating fuel economy on certain 2011, 2012, and 2013 models.

This was reported to be the largest penalty ever issued for a violation of the Clean Air Act, and came after the two carmakers compensated owners of those models as well.


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