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.
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.
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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