When Ford launched its all-new C-Max hybrid last fall, it was meant to be the automaker's big challenge to Toyota's Prius, which has has been far and away the leader in hybrid sales with the strongest brand.

But there are mounting complaints against the C-Max. It's not for the way the car drives, or looks (AOL Autos recommends the car), but rather how difficult it is to achieve the lofty 47 mpg fuel economy the company advertises. Numerous people on owner forums report getting significantly lower fuel economy than expected. And two California law firms have consolidated lawsuits against Ford alleging the company's C-Max marketing campaign is misleading.

Redlands, Calif.-based law firm McCuneWright is seeking punitive damages on behalf of hundreds of C-Max owners because of potentially overinflated fuel-efficiency claims, and said it will consolidate with a similar lawsuit filed by San Diego-based Robbins, Geller, Rudman and Dowd.

AOL Autos has tested the C-Max this past week, and this is what we found. In principal, it is possible to reach something like 47 mpg, and we have found several owners on Internet forums such as www.fordcmaxhybridforum.com and www.cmaxhybridowners.com who have done so. But we never did achieve close to 47 mpg in our week of driving in and around Ann Arbor, MI and commuting a few times on the highway to Detroit Metro Airport and the AOL office in Birmingham some 50 miles away.

Ford's chief engineer on the C-Max John Davis explained to us that several factors can hold fuel economy back from reaching the magic 47 mpg. During the break-in period of a new C-Max, fuel economy can be held back by a good 5 mpg. Cold weather can retard fuel economy by another 5 or so mpg. Maintaining a cabin temperature of around 72-degrees, while it is 40 degrees or below outside, for example, can hurt fuel economy because the engine will be cycling more often to keep the cabin warm. Driving above 70 mph will also hold back fuel economy.

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In order to actually reach 47 mph in the C-Max Hybrid, says Davis, it requires that the driver be very engaged in a series of driving habits and inputs to maximize fuel economy, including a lot of letting up on the throttle, not punching the accelerator and keeping speed below 60 mph. But Davis concedes, "Not everybody wants to drive that way."

AOL Autos achieved an average of 32 mpg after six days of mixed driving. The temperature was frequently below 30-degrees, and we did keep the cabin between 65-72. We did not set out to maximize the fuel economy, and probably could not have, given the weather in Michigan in February. We just drove it in a way that we thought was normal.

The power of advertising

Advertising 47 mpg is very important to Ford even if relatively few people can or will achieve it. "Fuel economy is probably the most important headline we can advertise," said Ford's global marketing chief James Farley at the launch of the C-Max. "When you can lead in fuel economy, consumers translate that to quality."

Ford's Davis says he does not believe Ford will let up the throttle on advertising the 47 mpg claim, because, "it is possible and we have seen and talked with a lot of owners who are getting it." Davis also said that Ford complied fully with the Environmental Protection Agency regulations for stating fuel economy.

Rich McCune of McCuneWright told the The Detroit News that his firm has received hundreds of complaints from C-Max owners. The suit originated with the experiences of Richard Pitkin of Roseville, Calif., who purchased a C-Max Hybrid in October. Pitkin says he averaged only 37 miles per gallon -- much lower than the EPA estimate.

Ford is not the first to be targeted by lawyers or to receive complaints about fuel economy. Hyundai and Kia in recent months have given owners credit cards for gas to make up for differences between advertised fuel economy and real-world fuel economy that the companies admitted resulted from flawed testing. Toyota, too, has been the target of class-action lawyers making similar clams against the Prius going back to 2004.

One of the reasons, says Ford's Davis, that the C-Max's 47 mpg is tricky to achieve is that the car was engineered for more driving fun and power than, for example, Prius and Honda Civic Hybrid. "We engineered in better driving characteristics to the C-Max than our competition has, and our customers tell us they like having the options," says Davis.

In other words, the C-Max allows true high-fuel-economy "geeks" to do all the things recommended to maximize fuel economy (and there are dashboard read-outs that tell the driver how they are doing and how they can do better), or the car will respond to sudden needs of acceleration and being tossed around like a BMW. The Prius is a notoriously joyless car to drive unless the owner is all about fuel economy.

C-Max so far is not a barn-burner for Ford. It sold 3,183 in February, about half as many Mustangs it sold last month. But C-Max is a new brand, and the car is still in its launch period.

For Ford, the trick going forward will be meeting and managing its customers' expectations.