The Ford Fiesta could become the best fuel economy play Ford has to meet demand and interest for more fuel efficient vehicles. And the long-awaited ad campaign ushering the new sub-compact to the marketplace will consistently remind potential buyers that it beats all rivals in its class including those from Toyota and Honda in features as well as miles-per-gallon.

The Fiesta has been the most hyped car in recent memory by any carmaker. For 20 months or so, Ford has been running social media efforts to warm up the U.S. market for the arrival of the car, which has been selling in Europe and Asia since last year with great success. The last car Ford sold as the Fiesta in the U.S. was a dinky somewhat tinny sub-compact, which dealers sold between 1978 and 1980.

The new Fiesta is a significant car that is part of Ford’s new world-car strategy. The car is only nominally different market to market around the world to meet varying safety and emissions standards, plus a few tweaks to address local styling tastes.

The car goes on sale this summer. Already, Ford has tagged the fuel economy at 29 city and 40 highway and the highway mileage will be featured heavily in virtually all communications no matter what prevailing gas prices are. The number-one buying consideration of shoppers in the sub-compact car, or B-car, market, says Matt van Dyke, marketing communications manager for Ford, is fuel economy.

Ford has set a new standard for marketing via social media for the Fiesta. Starting with the Fiesta Movement, which began in early 2009, when Ford tapped TK people to drive prototype Fiestas and share their experiences online, the company has achieved a 60% awareness level for the brand before the first conventional ads have run, or the car is even in dealerships. “By the way we measure these things, this has been five times more efficient spend of the money we have invested so far than any other launch,” said van Dyke.

The theme of the ad push, which starts May 18 on the broadcast of American Idol, revolves around the theme, “It’s A Pretty Big Deal.” The first ad revolves around two people sitting in a Fiesta talking about the car’s push-button start. After pushing it, a whimsical world unfolds around the two occupants with all the product attributes popping up in fun ways. See the ad here:

Print ads carry messages like: “The Fiesta gets 40 miles per gallon. 21 hybrids do not.” “The Fiesta has enough new world technology to put a 50-grand car to shame.”

Ford has been pushing mostly very rational advertising around models like the Fusion and Taurus. But the whimsy around Fiesta ads, which includes Internet webisodes like one one in which a zombie chases owners of a Toyota Yaris and Honda fit into their cars. Because neither car has quick, easy push-button start, the zombie was able to catch up with the drivers. The owner of the Fiesta in the webisode is able to escape the zombie. Toby Barlow, chief creative officer of Team Detroit, Ford’s ad agency, says the Fiesta lent itself to more humor and whimsy. “We still convey the product benefits, but the youth focus of the brand definitely called or a different approach than we have taken with our other new vehicles.”

Ford has stayed with its “Drive One” campaign since 2008, and plans to keep it going indefinitely. Indeed, since Ford chief marketing officer James Farley took over marketing at Ford in 2007, the company’s advertising has been much more focused and consistent. Before that, the company had gotten into the pattern of changing ad strategies and even taglines and themes every 12 to 15 months.

Another tongue-in-cheek Web video pits the Fiesta against a Lamborghini. In this video, as in others, Ford uses its Fiesta “agents” who were part of the Fiesta Movement social media campaign, to act. Brittani Taylor, for example, in the Lamborghini comparison video, amassed more than 300,000 subscribers to her Youtube videos, and 46,000 Twitter followers.

The Fiesta raises the bar in a big way in the sub-compact market. Prices start at $13,320 for a sedan, and $15,795 for a five door. Ford expects the split between the two versions to be about 50/50, though pricing for up-market featured five-door can get North of $20,000.

So far, 11,000-plus people have put down deposits for the first Fiestas.