On the record, and even off, auto manufacturers are usually fairly discreet about their competitors.

But starting this year, we've heard more open mutterings from several makers on the topic of gas mileage. "Our cars achieve their EPA ratings in real-world use," they'll say pointedly. "Not like some of our competitors."

Real-world Elantra mileage differs?

Now the dispute over whether and whose EPA ratings reflect real-world fuel efficiency has broken into the open.

The Consumer Watchdog organization, located in Santa Monica, California, called yesterday for the EPA to re-test the 2011 Hyundai Elantra compact, which is rated at 29 mpg city, 40 mpg highway, for a combined gas-mileage rating of 33 mpg.

2011 Hyundai Elantra

2011 Hyundai Elantra

"A trail of disappointed drivers" only achieves mileage ratings in the mid-20s under real-world conditions, says Judy Dugan, research director for Consumer Watchdog, citing online discussion forums with Elantra owners, and published results from road testers at USA Today, Motor Trend, and the 20-mpg city mileage recorded by Consumers Union.

The organization asks the EPA to test the Elantra in its own facility. If EPA results vary from the existing figures, it asks the agency to levy penalties on Hyundai that would include " fines, notification to buyers of its recent Elantra models and rebates that cover drivers’ added cost of fuel for average yearly miles driven."

Hyundai: 'stands by the numbers'

Jim Trainor, Hyundai's national manager of product PR, said the carmaker "stands by the EPA numbers," and pointed to the 39-mpg highway figure achieved by Consumers Union in a 2011 Elantra.

2011 Hyundai Elantra

2011 Hyundai Elantra

He declined to say whether Hyundai would have a formal response to Consumer Watchdog's request, noting that the story broke only late last night.

Your mileage may vary

In our own case, we tested a 2011 Hyundai Elantra sedan last April. Our overall mileage figure was between 34.2 mpg, or right on the EPA combined rating. We had just tested a 2011 Chevrolet Cruze Eco with six-speed manual too, also rated at 33 mpg, which which we got 34.4 mpg.

Across dozens of test cars, we usually hit the combined EPA rating and often get fuel efficiency figures that are 1 or 2 mpg higher, since our road test route has more high-speed driving than stop-and-go urban and suburban miles. Our experience with the Elantra pretty much stayed true to that rule.

2011 Chevy Cruze Eco and 2011 Hyundai Elantra during road tests (video frame capture)

2011 Chevy Cruze Eco and 2011 Hyundai Elantra during road tests (video frame capture)

We should note here that we do not "hypermile," or drive to wring every drop of energy out of gasoline. Instead, we want to give readers a sense of how a new car behaves in average real-world usage.

Self-certification

It's worth noting that the automakers submit self-certified results to the EPA; the agency does not test every car model, engine, and transmission combination--each of which is separately rated--every year.

Some automakers are now quietly discussing whether they should ask the EPA to certify the results they achieve--perhaps those for their most fuel-efficient vehicles, because high MPG figures have become such a marketing draw.

Live by the sword...?

Hyundai has aggressively promoted its EPA mileage ratings, going so far as to challenge other automakers to report their monthly sales of cars rated at 40 mpg or better.

2011 Hyundai Elantra

2011 Hyundai Elantra

No other maker does that, in part because their 40-mpg-rated models are often specific trim levels of model lines, usually at an extra cost, with lower ratings for the base vehicle.

Ford has its SFE models of the Fiesta and Focus, for example, and Chevrolet has its Cruze Eco (and soon a 2013 Malibu Eco too).

We can't help but wonder if this will be a case of "live by the sword, die by the sword."

Tell us your thoughts

We'll keep you posted on the outcome of Consumer Watchdog's request. Meanwhile, tell us what you think: Is Hyundai gaming the gas-mileage ratings system?

Leave us your thoughts in the Comments below.

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