Luxury buyers haven't paid much attention to diesels. Both BMW and Mercedes-Benz have tried ad campaigns to boost sales of their advanced diesel-powered luxury cars, but they didn't seem to make much of an impact on sales. Today, Audi starts its own "public awareness campaign" -- with a big advantage.

That's because for the first time in memory, diesel fuel cost less than gasoline. It also helps, too, that fuel prices are rising, putting fear of high gas costs back on the list approved topics for summer cocktail party chatter. The average price of a gallon of gas is $2.69, AAA says. By contrast, Diesel is now six cents cheaper at $2.63.

Until now, luxury car makers were limited to selling their advanced diesel models by touting their increased torque, quiet performance and increased driving range. None of it seemed to stick. When Open Road visited BMW North American CEO Jim O'Donnell in April, he expressed disappointment that diesel wasn't catching on faster. It was only a couple years ago that all the German automakers were insisting that diesel was a better gas-saving technology than hybrids and that sales were sure to take off.

Audi, with its big, $50,900 Q7 diesel SUV, will push diesels as a way of freeing the U.S. from dependence on foreign oil (see USA TODAY Q7 Test Drive here). The Q7 will be joined by an A3 diesel sedan in the fall. There will be ads on TV and stickers on gas pumps around the country. To see them, click here. The campaign, too, will push efficiency and 700-mile range from a single 26-gallon fillup.