Analysis: EPA Revising Fuel Economy Testing Guidelines

Derek Kreindler
by Derek Kreindler
analysis epa revising fuel economy testing guidelines

After a series of scandals involving incorrect fuel economy ratings, the EPA is revising its self-reporting guidelines for auto maker fuel economy standards, in a bid to ensure greater accuracy in the real world.

Currently, manufacturers are responsible for conducting their own tests according to EPA guidelines. While the new regulations cover the preparation of the vehicle in advance of the test, the Detroit News also reports that a key metric is being revised to closer match real world driving conditions

Also at issue are “road load” tests used to determine the impact of aerodynamic drag and tire rolling resistance on gas mileage. Currently, that is measured at 50 miles per hour. Under the new guidelines, automakers must measure the results at all speeds up to 70 mph.

The relatively slow speeds can often equal a highway fuel economy figure that is optimistic compared to what drivers can expect in real world conditions. The EPA also intends to close the loophole used by Ford that allowed it to assign the same fuel economy ratings for the C-Max and Fusion Hybrid models. This loophole allows auto makers to state the fuel economy rating of the “volume” model for a group of vehicles that use the same powertrain. In this case, Ford was able to use the superior Fusion’s rating for the C-Max (which got 43 mpg to the Fusion’s 47). Ford ended up re-stating fuel economy figures for the C-Max and compensating owners for delivering poorer than advertised fuel economy.

But the new guidelines are just that. Speaking to the paper, the EPA’s Chris Grundler said that drafting new, legally binding rules would take two to three years, which is too much time in their eyes

“Writing regulations takes time…When you are working in the rapidly changing environment that we’re in right now, we want to make sure that we are agile enough and flexible enough to change with those times.”

As we’ve noted in the past, the EPA’s fuel economy standards need a significant overhaul. The new “guidelines” simply don’t go far enough. The EPA only audits around 10 to 15 percent of vehicles per year, relying on the manufacturers to provide accurate claims for the rest of the fleet. Meanwhile, the test procedures themselves can be gamed due to powertrain calibration that takes advantage of the test parameters.

The test itself, as some have suggested, is really oriented more towards emissions than fuel consumption. If that’s the case, why not overhaul it to be more like the European tests that measure CO2 – which happen to be undergoing their own revamping right now to better ensure real world relevance? Both tests also give far too much leeway to small turbocharged engines, which are notorious for performing well on the test and then wildly missing their stated fuel economy in the real world.

With fuel economy figures becoming an increasingly important part of consumer decision-making – and auto maker marketing campaigns, the need for a more accurate fuel economy testing procedure has never been greater. The new guidelines are a step in the right direction, if nothing else. But they could go further.

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4 of 24 comments
  • Brian P Brian P on Feb 24, 2015

    Changing the test procedure itself is a lengthier exercise, but it needs to happen. The "correction factors" that they apply to the measurements don't fully address the problem. The current test cycles use extremely gentle acceleration and low speeds, and this problem exists both in USA and Europe. It allows hybrids to run electric-only for an unrealistic portion of the cycle, and it allows tiny, turbocharged engines to do the test cycle without running under boost. Include in the test cycle a step-change from zero to 70 mph / 120 km/h or thereabouts, and have the car follow the best it can (i.e. full throttle acceleration) and that all changes ...

    • See 1 previous
    • Speedlaw Speedlaw on Feb 25, 2015

      @Truckducken Yes, the upshift light in my SAABS, which I'm pretty sure was calibrated for a diesel engine, not a peaky turbo. I covered it with tape. Useless device.

  • Big Al from Oz Big Al from Oz on Feb 25, 2015

    The EPA fuel rating is a farce, the manufacturers know this. I do believe many of the FE figures are quite optimistic. My mother is complaining because she claims her Focus isn't returning the FE that was advertised. I agree with APaGttH that an independent testing agency should test the vehicles at the expense of the manufacturer. That is every model and trim. This would probably be cheaper than the manufacture testing the vehicles. At best the EPA FE figures only indicate that fuel efficiency has improved, for now, this will change. If the current system is maintained the FE figures will become more distorted. This distortion will be created by the increased use of turbo charged engines.

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  • Inside Looking Out This is actually the answer to the question I asked not that long ago.