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Update: EPA Considering Revising Test Procedures, Track Audits, to Improve Fuel Economy Ratings

It’s a well-known fact that the gas-mileage or range per charge that your car gets in real life will probably be a fair bit different to the official ratings given on the EPA-mandated window sticker. If you’re lucky, you’ll find your car exceeds EPA ratings, but more often than not, it will fall short.

EPA ratings are notoriously difficult to achieve in the real world.

EPA ratings are notoriously difficult to achieve in the real world.

Fuel economy ratings have traditionally been calculated by automakers in a laboratory following a series of very strict but short test cycles, with the EPA only actually carrying out additional test verification for about 15 per cent of all cars tested. As a consequence, test results have not only been exaggerated by automakers, but bear no resemblance to the real world.

If the EPA gets its own way however, that’s about to change, thanks to a proposal which would mandate that all automakers physically test their mileage claims in the real world, on real test tracks instead of on rolling roads in laboratories or computer simulations.

As The Wall Street Journal  details, the EPA wants to introduce regulation requiring all automakers to test fuel economy on a test track outside of the laboratory, measuring air temperature and pressure at the time of the test, as well as rolling resistance between the car’s tires and the test track.  While testing outside of the laboratory will induce more variables due to the effect of weather, it is hoped the tests will make it possible to more accurately predict fuel economy and range for a given set of real-world conditions.

[EDIT: We’ve just received clarification from the EPA on future changes to the fuel economy tests. Rather than creating public roadway test procedures to replace lab testing, the EPA is considering requiring automakers to undertake additional test track audits of their vehicles to help validate and augment data for the test procedure. You can see the official statement from the EPA at the bottom of this article.]

According to the EPA, some automakers already do carry out real-world track testing of their vehicles to better improve official gas mileage and range figures. But many automakers don’t, resulting in major discrepancies between real-world fuel economy and test cycle figures. As a consequence, we’ve seen many legal battles between angry owners and automakers after owners discovered that the claimed mileage figures of their brand new car were impossible to achieve in the real world.

How far you can drive in the real world per charge may not be the same as the official EPA figure.

How far you can drive in the real world per charge may not be the same as the official EPA figure.

Most noticeable among these are Ford and Kia, both of which have been forced by the EPA to drop their mileage claims for various models — including hybrids — after owner outcry.

Before it can be added as a regulation, the proposed change to EPA rules will go through a public consultation process, where both members of the public and automakers will be able to comment on it. If passed, it should make fuel economy ratings far more accurate, but here at Transport Evolved we think official test cycles need a dramatic change before fuel economy figures are truly realistic.

First of all, test cycles need to be extended over a more wide and varied set of road conditions to better mimic the normal commuting situations of everyday car drivers.

Second, test cycles for electric vehicles need to examine range over a larger portion of a car’s battery pack and in a variety of temperatures, since range is dramatically affected by exterior temperature, state of charge, and road conditions.

Sadly however, it’s impossible for automakers or the EPA to test for every eventuality, meaning no matter how good the fuel economy and range tests get, there will always be a margin of error.

And in an electric car where the total energy carried on board is the equivalent of a few gallons of gasoline, that margin of error will always be more noticeable.

[UPDATE: We’ve just received the following statement from the U.S. EPA, detailing a little extra clarification on the matter of the proposed regulatory change.

Some recent press articles have suggested that EPA is considering requiring automakers to do “road tests” and/or “real world tests” to validate fuel economy label values. EPA fuel economy labels are based on sophisticated laboratory testing, which allows precise control of many important variables that can affect fuel economy, and which yields data that are consistent, accurate, and repeatable in a way that real world driving can never be.  EPA wants to clarify that we are not considering creating public roadway test procedures to replace laboratory testing.  Rather, EPA is considering requiring automakers to perform supplemental test track audits of production vehicles to validate the values for aerodynamic drag and tire friction, which are important data inputs for our laboratory fuel economy testing.  Augmenting EPA’s existing pre-production procedures with post production audits of real world factors will help further ensure that the data used in EPA labels accurately reflect the vehicles consumers find on dealer lots.


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  • Ad van der Meer

    Testing in the “real world” is impossible to do. Should all OEM’s bring their new cars to a track on the same day to test under exact same conditions. Should the EPA offer a testdriver to do all the tests to eliminate that variable? Does the EPA think it can creat a mathematical model to compare the numbers from different OEM’s testing their cars on different tracks under different conditions? Good luck!nI think the lab is the right place to do the tests where conditions and variables can be controlled in a manner that can be replicated all over the world. The conditions of that test should be the subject of the discussions. EPA 5 is an improvement over the old EPA standard, but maybe EPA 5 is not even realistic enough.nThe consequences of not being able to reproduce the fuel consumption with a car of a randomly selected dealer lot should be harsh enough to make the OEM’s think twice about cheating with the numbers.

  • John Briggs

    Nice addition

  • lad76

    The MPGe is a confusion factor. In fact he whole sticker is busy and difficult to understand. You can condense it all down to one simple test; run a warmed up car at 30 mph on a dyno and check its mileage; then run it at 65 mph and check the mileage. That takes care of the major factors except aero drag, which can be calculated as a negative factor using the 65 mph speed, the frontal area and the CD. EVs should be in kilowatt hours per mile and fossil cars in mpg. The range of the car and the cost of “fuel” can then be calculated and indicated. Continuing to creating a new set of EPA tests each year deletes the whole idea of quantifying mileage data for comparisons.

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