Survey: Gas prices drop as summer nears

CAMARILLO, California (CNN) -- The cost of self-serve, regular gasoline has slid nearly 2.5 cents across the country in the last three weeks to a national average of $1.40 per gallon, according to a survey released Sunday.

The cheapest gas was in Tulsa, Oklahoma, where the average gallon of self-serve regular was $1.16, said Trilby Lundberg, whose Lundberg Survey of 8,000 gas stations was conducted between May 17 and Friday.

Chicago had the highest average self-serve price, $1.63, Lundberg reported.

Declining crude oil prices and sufficient supplies are behind the decline, Lundberg said. On average, prices are about 29 cents per gallon lower than at this time last year, she said. At that time, the average price was $1.69.

June is usually the peak month for driving -- because of vacations and other reasons, Lundberg said.

"It's a big wives' tale to say the prices always jump in the spring and summer" because more people are on the road, she said.

The $1.40 national average for self-serve, regular gas includes 41.5 cents in federal, state excise and other taxes, Lundberg said.

Other per-gallon prices around the nation are: