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Fuel Efficiency Ratings — possible lemon law issue?

Recently, a concerned consumer in Houston, Texas contacted my law office about a new truck he had recently purchased. He was concerned that his vehicle might be a lemon because he had never been able to obtain the mileage that was shown on the information sticker when he purchased it. He wanted to know if there was any recourse under the state (Texas) lemon laws or fraud statutes because his vehicle appeared to fail to live up to the advertised specifications.

Without determining the strength or validity of any possible legal claims arising from this situation, lets take a few minutes to look at how those fuel efficiency numbers are obtained and why they are there.

The Environmental Protection Agency (EPA), part of the federal government, requires that car manufactures test vehicles to determine their fuel consumption rate. Not every car produced is tested — only a representative vehicle for the specific model. Typically the vehicle tested is a prototype — before production is started. Some very large vehicles (as well as motorcycles) are currently exempt.



Vehicles are tested during simulated driving in a laboratory environment. The car is placed on a dynamometer (rollers under the wheels). The force needed to turn the dynamometer can be varied, thereby simulating different environmental conditions (e.g. headwind, uphill etc). While the car is on the dynamometer, the exhaust from the engine is collected and the amount of carbon emitted is measured. This amount is used to calculate the amount of fuel that is being consumed. The car is “driven” through a series of “courses” that are designed to mimic different types of driving conditions. Examples of the routes can be found at the Fuel Economy site.

The EPA provides the methods and procedures used to test vehicles, but it is the manufacturers themselves who perform the tests. The EPA does check these results, independently testing 10-15% of the results. If you would like to read further about this, or look up ratings for your car, go to:

So, will you ever achieve the fuel efficiency shown on the sticker on your new car? Chances are probably not. These values are obtained in ideal test settings with well-tuned prototype cars. “Ideal” drivers are used who never turn the radio on, never use the a/c, don’t speed and don’t rev the engine. In reality there are car-to-car variations, many real life driving situations, and numerous other factors that are not controlled. However, the fuel efficiency numbers are very useful in comparing different makes and models of cars to each other, as well as for obtaining a general idea of how efficient a car might be.

Starting in 2008, the procedures for testing cars will be modified to take into account the use of air conditioning, faster acceleration, and colder ambient temperatures.

Since the government mandates that these tests are performed and displayed on cars that are for sale, it is unlikely that you can hold the dealer or manufacturer responsible for discrepancies between what was displayed and what you experience. You might be better off to contact your elected representatives and press and demand more realistic testing standards and requirements.

Of course if your vehicle is a lemon, it may have defects that deleteriously impact fuel consumption.

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