American Honda’s recent loss in small-claims court to a Southern California woman who argued she was misled about the fuel efficiency of her ’06 Civic Hybrid does not bode well for five class-action suits the auto maker still faces regarding the mileage of ’03-’09 Civic Hybrids.

Honda also faces a potential onslaught of disgruntled Civic owners who may decide to take their cases through the small-claims system after learning Heather Peters was awarded $9,867.

However, the ruling, which Honda plans to appeal in Los Angeles County Superior Court, also is spurring calls for the federal government to rein in the way the industry assigns fuel-economy estimates on the window stickers of new cars and trucks.

Such changes would make the miles-per-gallon rating process more fair for both consumers and auto makers, Judy Dugan, research director for Consumer Watchdog, a California-based consumer-rights group, tells WardsAuto.

In his award to Peters, Los Angeles Superior Court Commissioner Douglas Carnahan acknowledged a list of misleading representations by Honda that the plaintiff identified correctly.

These include claims the ’06 Civic Hybrid, which Peters still owns, would use “amazingly little fuel;” provides “plenty of horsepower while still sipping fuel;” and “save plenty of money on fuel with up to 50 mpg (4.7 L/100 km) during city driving.”

Peters says the car only averages about 30 mpg (7.8 L/100 km).

Dugan cites comparative research between the ’11 Chevrolet Cruze Eco and ’11 Hyundai Elantra’s, both of which were assigned a combined city/highway fuel-economy estimate of 33 mpg (7.1 L/100 km) by the Environmental Protection Agency.

This, despite the fact the Cruze Eco’s fuel efficiency has been found to be 28% better than the Elantra, according to statistics compiled by Feully.com, which collects comparative mileage data on an array of vehicles from individual drivers who visit the site and self-report their fuel consumption.

The study also shows the Elantra fell 12% below the EPA’s 33-mpg estimate in the ’12 model and 3% less in the ’11 model.

Consumer Watchdog, founded by attorney Harvey Rosenfield, points out a car reviewer at a major daily newspaper wrote in September that he was “disappointed” that his new ’12 Elantra only averaged 22 mpg (10.7 L/100 km) in combined city/highway driving.

“If a shopper looks at two similar cars of nearly equal price and one claims 3-4 more miles per gallon in combined driving than the other, as is the case with the Elantra and the Cruze, the smart driver will pick the more-efficient car,” Dugan says.

The marketing disadvantage to General Motors’ Chevrolet Div. “is obvious,” Dugan writes in an early January letter to the Obama Admin. “Elantra gets to advertise higher miles per gallon than the Cruze, even though the Cruze gets equal or better (mileage) once it rolls off the lot.”

Dugan continues in the letter that since “the line between hybrid and conventional vehicles is blurring,” it’s “all the more important that EPA-certified numbers be fully dependable from model to model and from one engine type to another.”

She says consumers would be shocked to find out the EPA does not conduct most of the clean-air and fuel-economy tests it approves. Instead, individual auto makers administer the tests and send the results to the government agency, which retests about 15% of the models.

Peters’ victory in California against Honda “raises consumer awareness of the mpg gap issue,” says Dugan, but it nonetheless will require continued pressure on government officials to get the EPA to act.

Then there are the auto makers that, despite strong evidence the current fuel-economy-rating system has and will hurt sales, “deny, deny, deny” there’s a problem, says Dugan.

The Peters ruling has helped open the legal system to other Honda owners with less dramatic cases, she says. Equally important, the case shows through example how consumers can educate themselves better understand the auto market and stand up for themselves.

Buyers then will see “some cars do meet the (fuel-economy) standards better than others,” Dugan says. “Not all cars have problems.”

But for owners whose cars do not meet expectations, the industry needs to become more responsive. “Consumers feel cheated,” she says. “They are being cheated, and the government needs to fix this.”

In an interview with WardsAuto last month, Hyundai’s U.S. CEO John Krafcik cited Elantra owners’ city-centric commutes as the reason some were not seeing fuel-economy closer to the window-sticker figures.