NEW YORK (CNN/Money) - Ford's new Five Hundred sedan earned the best possible score of five stars for front and side impact protection for occupants in all seating positions, according to new test results of 2005 models released Tuesday by the National Highway Traffic Safety Administration.

Ford Five Hundred

The Mercury Montego, a corporate "twin" to the Five Hundred, was given the same score. The Acura RL sedan also got five star ratings for front and side impact protection in all seating positions.

The new Pontiac G6 got five stars for protecting occupants in front crashes but just three stars for protecting front and rear passengers in side impact crashes. The Ford Freestyle, an SUV-like wagon similar to the Five Hundred sedan, has not yet been tested for front crash protection but received five star ratings for side impact protection.

Among rollover test results that were also released Tuesday, the Lincoln Navigator and Toyota Highlander were said to have the lowest chance of rolling over in a single vehicle crash. They were computed to each have a 17.4 percent chance of rolling over and neither tipped up in the agency's dynamic driving test.

Among the vehicles tested in this round, only the Chevrolet Equinox, in both 2-wheel drive and 4-wheel drive versions, tipped on the driving test. Still, the Equinox was not the vehicle with the highest chance of a rollover in the real world among those tested in this round, according to NHTSA.

The Equinox was still given four stars, the highest star rating given to any SUV, for rollover resistance. That is because of its high "Static Stability Factor," a number computed by comparing the height of the vehicle's center of gravity to its width. That number carries more importance in NHTSA's rollover rating system than the driving test does.

The 2-wheel drive Equinox has a 19.1 percent chance of rolling over in a single vehicle crash, according to NHTSA's calculations, and the 4-wheel drive version has a 20.4 percent chance.

Chevrolet Equinox

The Ford Explorer and it's corporate "twin," the Mercury Mountaineer, were computed to have a 24.6 percent chance of rolling over in a single vehicle crash and, as a result, were given three stars for rollover resistance. The Explorer/Mountaineer did not tip up NHTSA's dynamic driving test.

The Ford Freestyle, which the agency counts as a van, had just a 14.7 percent chance of rolling over in a single vehicle crash, according to the agency. That was lower than any of the other vans tested.

The Chrysler Town & Country and Dodge Grand Caravan minivans were computed to have a 17.4 percent chance of rolling over.

The agency also tested several cars for rollover resistance. The most stable of those was the Ford Mustang, which has an 8.7 percent chance of rolling over in a single vehicle crash, the agency said.

For more information on crash test results and rollover ratings, go to NHTSA's Web site, safercar.gov.