BLOOMINGTON - For years, Chelsea Childs bought season passes to Six Flags St. Louis to spend time with friends and family, but the tradition ends this year.

With gas prices reaching $3.20 a gallon in the Twin Cities on Friday and potentially increasing more this summer, the cost of getting there is just too high, said Childs of Normal. She's also cut down on trips to Peoria.

"I just can't go out of town much anymore, especially because I have a big car that takes a lot of gas," said Childs, while putting $10 of gas in her minivan Friday at Thorntons on Main Street, Bloomington.

While unleaded gas topped the $3 mark last July, it hasn't hit the $3.20 mark since Hurricane Katrina disrupted refinery output in the Gulf Coast in fall 2005. That year, prices hovered above $3 for about a week before inching down slowly.

Steep spikes in gasoline, like the 20-cent increase Friday, are typically tied to sudden events like Katrina, but not this week. Experts could not tie the increase to one event.

Prices could hedge upward even more.

Bill Fleischli, executive vice president of the Illinois Petroleum Marketers Association in Springfield, did not discount the possibility of $4 gas sometime this summer.

"For the 12th consecutive week, stocks of U.S. (gasoline) have declined, and that's not a good omen," Fleischli said.

Refining problems in Indiana and Oklahoma have reduced output, he said, while demand continues to rise.

Output has also dropped as refineries switch to a special summer blend of gasoline, said Nicole Niemi, a spokeswoman for AAA-Chicago Motor Club. Gas spikes each year during this conversion.

Gasoline stocks are down about 10 percent this year, according to the U.S. Energy Information Administration in Washington D.C., while demand is up 2.3 percent.

Demand typically only rises 1.2 percent each year, Fleischli said.

In addition, crude oil is up about $15 per barrel this year, she said, from a low of around $50 a barrel earlier this year. Crude oil traded at $63.25 per barrel early Friday on the New York Mercantile Exchange, before dropping to $61.77 a barrel late Friday afternoon.

Gasoline didn't top $3 last year until early July. At that time, crude oil cost $75.40 a barrel on the New York Mercantile Exchange.

Motorists don't seem to curb their driving habits, despite gas topping $3 in the Twin Cities and other areas.

Michael Rebinski and Rachel Nagelberg, for example, stopped in Bloomington to refuel Friday as they drive from Pittsburg to Kansas City and back.

"We're completing this road trip no matter what," said Rebinski, a student at the University of Pittsburg. "We just hit the 1,000-mile mark, and I think we'll go 3,500 miles."

At $3.20 per gallon, in a car that gets 25 miles per gallon, that's a $448 trip, in gas alone.

Some people can't cut back travel.

Jennifer Barnard of Normal doesn't drive out of town much for leisure, but her job at the Marc Center in Normal forces her to travel throughout Bloomington-Normal every day.

"But I make my boyfriend drive me around," she joked.