AUBURN - Sure, Charles Casey loved his pickup truck. It was, after all, just a couple of years old. It had a V-6. It was great for hauling stuff.

But with a stroke of the pen Friday, the Buckfield man dumped his 2006 Toyota Tacoma at Emerson Toyota-Scion in Auburn and picked up a 2009 Toyota Corolla. He just couldn't live with the gas cost anymore.

Truck: 20 miles per gallon

Car: 35 mpg.

"It works for me," Casey said.

With gas prices climbing - AAA listed Maine's regular unleaded average at $3.66 per gallon Friday, up 35 cents from the month before - Casey isn't the only one downsizing. Area car dealers say customers are streaming in to trade gas-guzzling trucks and SUVs for gas-sipping cars.

"At $3 (per gallon) it started to hit," said Jim Joys, general manager for K&R Auto Sales in Auburn. "Now, at the $3.50 mark, it's like the explosion point."

Joys noticed the trend starting about six months ago. Three-quarters of his inventory had been in trucks. Now his inventory is three-quarters cars. Imports and economy cars are particularly popular.

"There's a fundamental change going on right now. When people used to come in to buy their vehicles, they'd look at the car payment. Now they're actually looking at car payment and fuel payment. It's amazing," he said. "I've never seen this happen in 25 years in the business."

One customer with a long commute saved $500 a month when she got rid of her SUV and bought a car, Joys said.

At Emerson, where Casey traded his truck for a car, 4-cylinder, $15,000-plus Corollas are particularly popular. So is the Yaris, which starts at $11,500 and can get 35 mpg on the highway.

"Everybody's got their eyes on the window stickers of the cars and what the fuel economy ratings are," said Vinnie Goulette, Emerson's general manager.

In the Boston region, which includes Maine, sales of 4-cylinder Scions - which can get up to 33 mpg, depending on the model - have jumped 66 percent, according to Goulette.

"And they're saying good riddance. They're not taking it personal when their old truck goes," he said.

At the Lee Auto Mall in Auburn, new Honda Civics are popular. They start around $15,000 and can get up to 36 mpg, depending on the model. For used vehicles, customers want anything that gets in the 20s and 30s for gas mileage.

"When you're paying $500 and $600 a month to heat your house, you've only got so much money to go around," said Jeff Benton, used car manager for Lee.

At Goodwin's Chevrolet-Mazda in Brunswick, Chevrolet Impalas ($22,400-plus and up to 30 mpg) and Chevrolet Cobalts ($14,800-plus and up to 32 mpg) are in demand. They're replacing, among other SUVs, the Chevrolet Tahoe, which gets up to 18 mpg.

"They're thinking 'If my payment goes down a little bit, even if it goes down $30 a month, with fuel savings it's almost going to look like $100 a month,'" said Lance Miller, sales manager.

But while buyers are happy to get into more fuel efficient cars, they aren't so happy when they learn what their old trucks and SUVs are worth.

"They've dropped about 30, 35 percent," Miller said.

At K&R Auto Sales, Joys sees the downturn every time he goes to buy inventory at a vehicle auction. Seven out of eight vehicles are trucks and SUVs, he said. Bidding is sparse.

"If you look at guides and book values and things like that, the trucks are dropping so fast that the books aren't keeping up with it," he said. "And the cars are rising so fast that the books aren't keeping up with it."

Although demand for trucks and SUVs is generally falling, sales aren't dead everywhere.

Bessey Motor Sales in Paris has been selling trucks as well as cars. Contractors still want trucks to haul large loads and big families still want SUVs for the room.

"A lot of people can't alter their need," said dealer Gene Benner.

When Casey got rid of his Tacoma on Friday, he learned that his truck was still worth some money. As bad as 20 mpg seemed to him, it was good fuel economy compared to other, larger trucks. Demand for them has been so high that Emerson was completely sold out of Tacomas until Casey came along.

They gave him $17,000 for the truck, almost exactly what his new Corolla cost. And the change will save him more than $1,100 a year in gas.