U.S. car rental companies have been hit from all sides by the weak economy, and road warriors are feeling the impact when they pick up their vehicles.

Instead of getting a vehicle with low mileage and that intoxicating new-car smell, even frequent renters are being assigned older, road-weary cars.

"Once a month I'll get a car that has more than 20,000 miles on it," said Dan Hemmati, a management consultant from Washington, who rents a car every week. "Some of these cars are in really poor condition - stains on the upholstery, or the 'check engine' light is on. Even if you go in and try to switch, they'll tell you that's the best car they've got."

Executives at the car hire companies acknowledge their aging fleets, saying they face an unprecedented set of challenges: declining demand, tight credit markets that make it difficult to buy new cars, and a depressed market for used cars.

"The used-car market is so weak it would've been cost-prohibitive for us to sell into that market," said Richard Broome, a spokesman for Hertz, which on Tuesday reported a fourth-quarter loss as sales fell 16 percent.

Hertz and its competitors have been responding to the downturn by reducing the size of their fleets and cutting jobs. They have also been negotiating deals with a greater number of automakers, pursuing new opportunities like the car-sharing business model used by Zipcar, and holding on to vehicles longer. Hertz, for instance, now keeps cars in service for 20 months instead of 16.

"You really feel it in the performance of the car," said Jeremy Coyle, a payroll consultant from Hoboken, New Jersey, who recently rented a Chevrolet Impala that shuddered at 60 miles an hour.

Chris Brown, executive editor of the trade publication Auto Rental News, said that companies used to sell vehicles before they'd been driven 20,000 miles but are now keeping them up to 30,000 or even 40,000 miles.

"The industry in general is going through some contraction pains," Brown said, citing staff cuts and stricter enforcement of policies like return times as two other changes that have affected the rental experience.

A JD. Power & Associates survey of customer satisfaction with the car rental experience, released in November, found the average score declined for the second straight year after gradually increasing since 2003.

That survey was conducted before an industrywide round of layoff announcements in the past few months: 2,200 positions eliminated at the Avis Budget Group, 4,000 at Hertz, 400 at the Dollar Thrifty Automotive Group and 2,000 at Enterprise, a privately held company that also owns National and Alamo.

"For Enterprise to lay off people is very, very exceptional, while the other companies have traditionally done it over the years," said Neil Abrams, president of the Abrams Consulting Group, which advises car rental companies.

Abrams said the industry had been responding to the most difficult downturn he had seen in 33 years. He estimated that demand for rental cars was down 10 percent to 15 percent from a year ago, while the industry had reduced the size of its fleet by more than 15 percent. Yet he said companies still managed to raise rates. In his weekly survey of midsize car rental rates at 10 major U.S. airports, the average rate in late January was $78.58 a day, compared with $59.76 a year ago.