HACKENSACK, N.J. — So much for fuel efficiency!

A year ago, with gasoline selling for more than $4 a gallon, drivers abandoned their gas-guzzling trucks and large SUVs for high-mileage compacts. Now, with prices in the $2.50 range, they're going back to the big guys, at least in the used-car market.

That sharp U-turn in buying habits has led to a 5.8 percent increase in the price of used cars in the past year — including a 16 percent spike since the beginning of the year — and a shortage of the kinds of vehicles drivers were unloading last summer, according to the Manheim Used Vehicle Value Index.

To Richard Fernandez, the Manheim survey confirms what he sees every day at Fette Ford in Clifton, N.J., where he is the senior sales manager. Used-car sales are down more than 25 percent from a year ago, and he is unable to obtain some of the most popular models.

"Our used-car lot used to have twice as many cars," Fernandez said. Included is just one Expedition, the biggest and least fuel-efficient in the Ford inventory — and once again, among the most in-demand used cars.

"I can't even get them," he said. "No one is trading them in."

HIGHER PRICES

Dealers, who buy most of their cars at auction, have so far been able to pass higher auction prices on to retail customers, so the increase in wholesale prices has come without downside consequences to them, Manheim said.

"But, the cause of higher wholesale prices does stem from a negative — namely, the significant reduction in potential supply available to the auction industry," the report said.

The biggest price gains since last June were for pickup trucks (up 27 percent) and sport utility vehicles (25.8 percent), while compacts fell almost 10 percent and midsize cars were off by 3.4 percent.

The index has risen for six consecutive months, reaching a 22-month high. This year's price gain reflects a significant reduction in potential supply, as the sharp drop in sales of new cars and trucks means that fewer used vehicles are available as trade-ins, Manheim said.

New vehicle sales over the past 12 months have totaled only 10.7 million units, while sales for all of 2009 will be lucky to top 10.1 million, and, in 2010, sales will probably be in the neighborhood of 12 million, the report said.

"Thus, over a time span of 30 months, sales will have averaged less than 11 million vehicles per year versus an average annual sales pace of 16.9 million between 1999 and 2007," the report said.

"Simply put, the used vehicles of tomorrow are not being produced today."

OLD HABITS

The dynamics of used-car sales at new car dealers are different than those at used-car dealers such as State Auto Sales in Lodi, N.J., but the outcome is similar, owner Cato Angel said.

When gas was more than $4, it was a buyer's market for SUVs and pickups, he said. "They were giving them away."

Once pump prices fell, however, many consumers went back to old habits and fuel efficiency became less important.

Even so, overall sales are down, Angel said. "Everyone's feeling it."

Several factors have contributed to the vehicle shortage, in addition to the reduction of trade-ins, Fernandez said.

One is the government's new "Cash for Clunkers" program, which provides up to $4,500 toward the purchase or lease of a new car for consumers who turn in an old, inefficient car, Fernandez said. That could help boost new-car sales — which is the purpose of the program — but it means even fewer used cars on the market.

The dealer is not allowed to resell the clunkers.

Also, new-car dealers used to get a lot of leased cars for resale, "but we're not buying them," Fernandez said. Because of the high residual price — the result of lease deals built on low monthly payments — "it's not worth it to get them."