5. Jeep Liberty
> Decrease in units sold: 77,650
> Pct drop: 55.9%
> Base car price: $23,250
> Fuel efficiency: 16 city, 22 hwy

> JD Powers quality score: 2/5
> JD Powers reliability score: 2.5/5

The Liberty is the mid-priced model among the six that Jeep offers. The company currently offers more than one incentive to draw buyers — usually a sign that demand is low. Among these offers are zero percent financing for up to 60 months, and a $3,000 cash allowance. The Liberty was first introduced nine years ago. A new generation of the SUV was launched in 2008. Sales have declined since their peak in 2004.

4. Silverado 2500HD
> Decrease in units sold: 77,741
> Pct drop: 53.1%
> Base car price: $28,415
> Fuel efficiency: 12 city, 15 hwy
> JD Powers quality score: 3/5
> JD Powers reliability score: 3.5/5

The Silverado is Chevy’s flagship pickup. It competes with the industry leading Ford F-series and the Dodge Ram, along with several other pickups made by foreign manufacturers. The Silverado HD is the heavy duty version of the truck. It can pull a load of up to 17,800 pounds. The first HD models were introduced in 2001. Sales of the less-expensive Silverado 1500 have fallen by 21% over the past five years.

3. Mustang
> Decrease in units sold: 93,829
> Pct drop: 58.2%
> Base car price: $22,310
> fuel efficiency: 19 city, 31 hwy
> JD Powers quality score: 3/5
> JD Powers reliability score: 4/5

The high point of auto legend Lee Iaccoca’s career was not his revival of Chrysler but the launch of the Mustang in 1964. Many car industry historians say it was Ford’s fastest selling car since the Model A. Over 400,000 Mustangs were sold in the car’s first model year. The current version of the Mustang is the fifth generation of the automobile. Ford upgraded the Mustang engines this year, but that has not helped revive sales. The Mustang is in a highly competitive part of the market, which includes the Chevy Camaro.

2. Ford Taurus
> Decrease in units sold: 108,777
> Pct drop: 62.4%
> Base car price: $25,555
> Fuel efficiency: 18 city, 28 hwy
> JD Powers quality score: 4.5/5
> JD Powers reliability score: 3.5/5

The Taurus is one of the most successful Ford vehicles of all time. Its first model year was 1986, and Ford had sold one million units of the vehicle by 1989. The fourth generation of the Taurus was launched in 2000 and was discontinued in 2006 due to slow sales. Ford revived the Taurus in 2007, and upgraded it again last year.

1. Chrysler 300
> Decrease in units sold: 111,596
> Pct drop: 78.9%
> Base car price: $27,170
> fuel efficiency: 18 city, 27 hwy
> JD Powers quality score: 3/5
> JD Powers reliability score: 3.5/5

The 300 — a sports sedan first produced in 1999 — was the flagship car of the Chrysler model line in the middle of the last decade. The manufacturer sold a model under a similar name in the 1950s and 1960s. A new version of the 300 was released in 2005, but it has grown old quickly in the eyes of the consumer. The latest edition of the car was introduced this year, but sales have been modest.

Douglas A. McIntyre