DETROIT — Although there's a growing trend among automakers to recommend that drivers pump premium into their cars, Ford and General Motors are quietly touting the fact that some of their luxury models take regular gas.

Ford Motor's 2009 Lincoln MKS and General Motor's Cadillac CTS were both engineered to run just as well on regular-grade fuel as the high-octane stuff. By contrast, automakers recommend premium gas for nearly 62 percent of new vehicles on the market, up from 47 percent of models in 2002, according to Kelley Blue Book.

Both Ford and GM are encouraging dealers and their salespeople to play up their no-premium-gas cars to potential buyers worried about the high cost of gas. It could be a key selling point at a time when consumers are seeking more fuel-efficient cars. Premium fuel generally costs about 20 cents a gallon more than regular gas.

Stephen Russ, a technical leader with Ford's powertrain operations, says engines in the MKS and Ford Edge were designed to detect whether premium or regular fuel was added to the tank. Ford will roll out the technology on more engines in coming years, he says.

The Cadillac CTS, which was introduced last year, was designed for regular gas. "We could see that the cost of fuel was going to become an increasing issue," says Cadillac spokesman Kevin Smith.

Though premium gas is recommended for many models, most will run — with a little less horsepower — on regular gas. Knowing that, many drivers are filling up with regular despite automaker recommendations. Demand for premium fuel has fallen considerably in the past 10 years, down 52 percent in May 2008 compared with May 1998, according to the U.S. Energy Information Administration.

"There are two kinds of people using premium gas: Those who have a car that requires it, and the other kind is a person who likes to waste money," says Jake Fisher, senior engineer with Consumer Reports.

Luxury buyers, the ones who often get hit with premium-only vehicles, usually have deep enough pockets to afford the extra 20 cents per gallon.

"The automakers are hanging on to any idea that is remotely interpreted as gas efficient," says Jesse Toprak, director of industry analysis for www.Edmunds.com. "If you're considering buying a vehicle that requires premium and you are making a decision based on gas prices, you're probably buying the wrong car."