Until July, when gas prices rose to $4.11 per gallon for regular, the Big 3 automakers started putting less of an emphasis on gas-guzzling trucks and SUVs and started to ramp up production of smaller, more fuel-efficient cars.

According to the Environmental Protection Agency, GM has the market cornered for the most fuel-efficient American cars, holding nine spots on the top 10.

The Ford Focus -- the only non-GM car on the list, tied for the top spot with the Chevrolet Aveo and Pontiac Vibe, with a combined fuel economy of 28 mpg. The EPA bases its ratings on 45 percent of driving being on the highway, 55 percent in the city.

However, the top American cars still fall behind the Toyota Yaris at 31 mpg and the Honda Fit at 30 mpg.

In ratings compiled by Forbes.com, the Focus and the Saturn Astra got the same miles per gallon in an manual transmission car as an automatic. Manual transmission versions of the Aveo, the Chevrolet Cobalt and the Pontiac G5 got 30 mpg, but according to Mike Omotoso, an analyst at J.D. Power and Associates, manual transmission vehicles account for less than 10 percent of passenger-car sales per year.

Bringing more fuel-efficient cars to market quickly will be important, as automakers race to meet more stringent Corporate Average Fuel Economy standards mandated by the National Highway Traffic Safety Administration that must be in place by the 2010 model year. The combined fuel economy for an automaker's fleet of cars must exceed 27.5 mpg by 2010.

"In 2010, we will see a lot happening at the same time," Paul Lacy, manager of technical research at Global Insights, an analysis and forecasting firm, told Forbes. "We will see a greater penetration of diesel engines on the market, more hybrids and more flex fuel. All will hit the fan at the same time."

Chrysler, which doesn't have any cars in the top 10, announced that in 2010, Nissan will start building a new small car for the automaker.

"Chrysler has a few things up their sleeve that they haven't told us about," Lacy said.

10 Most Fuel-Efficient American Cars

1. 2008 Ford Focus, combined fuel economy of 28 mpg

1. 2009 Chevrolet Aveo, 28 mpg

1. 2009 Pontiac Vibe, 28 mpg

4. 2009 Saturn Astra, 27 mpg

4. 2009 Chevrolet Cobalt, 27 mpg

4. 2009 Pontiac G5, 27 mpg

7. 2009 Chevrolet Malibu, 26 mpg

7. Pontiac G6, 26 mpg

7. 2009 Saturn Aura, 26 mpg

10. 2009 Chevrolet HHR, 25 mpg