油价飙升，可有尽头？

MELISSA BLOCK, HOST: This is ALL THINGS CONSIDERED from NPR News. I'm Melissa Block.

Nationwide, the average price of gasoline has ticked up more than 30 cents a gallon since July 1st.

Scott Detrow, of member station WITF in Harrisburg, Pennsylvania, reports on the cause of the spike and whether an end is in sight.

SCOTT DETROW, BYLINE: If you plot out a chart of 2012's average gasoline prices, you get what looks like a roller coaster - the steady increase from January to April, the spring peak around $4 per gallon, and then a steady decline in May and June.

At the beginning of last month, the national average was about $3.42. But since then, that sharp roller coaster has been heading into its second big climb. Prices have been going up and up since July 1st, and are now approaching $3.80. So are we still climbing or near the peak?

Tom Kloza, the chief oil analyst for the Oil Price Information Service, thinks it's a short-term problem.

TOM KLOZA: This is something you'll have to put up with for a few weeks, maybe more if you're on the West Coast, but certainly not in the majority of the country.

DETROW: Two factors are driving the increases. The first, like always, is the price of crude oil, which has risen from around $80 a barrel to about $94 since June. The second factor is a bit more unusual, a series of problems in the United States' energy infrastructure have created kinks in the supply chain.

KLOZA: It's the end of the summer. Refineries have been running hard and running at high rates, and sometimes you get a cluster of breakdowns.

DETROW: A fire at a Chevron refinery in Richmond, California, was the biggest issue. But two Midwestern refineries also suffered equipment failures around the same time.

(SOUNDBITE OF A GAS NOZZLE)

DETROW: Due mostly to the Richmond fire, gas is already approaching $4 on the West Coast. The increase has been more subdued in places like Pennsylvania. So much so, that some drivers, like Marie Watson, who's filling up her car at a Harrisburg gas station, haven't even noticed it.

MARIE WATSON: I think it's gone down just a tad bit.

DETROW: They went down in the spring but now they're going back up.

WATSON: OK.

DETROW: Three pumps over, Anna Nielsen has noticed the change. But she says it has not affected her driving habits.

ANNA NIELSEN: It's just kind of something I deal with. I'm really lucky 'cause I get really good gas mileage.

DETROW: Nielson says she'd probably cut back on travel if gas tops $4 a gallon.

NIELSEN: Like, my mom lives in Lancaster and I probably wouldn't go see her as often. My best friend lives in Philadelphia. So, I probably wouldn't be doing as much of those longer trips.

DETROW: National driving demand typically starts to fall after Labor Day. So, barring a major disruption in oil or gasoline supply, like a major Gulf Coast hurricane, experts like Tom Kloza expect prices to start falling in mid-September, and stay down until the spring.

KLOZA: When the whole cycle starts again. In the fall and the winter, there's plenty of gasoline. We don't drive as much.

DETROW: The shift from summer to winter-blend gas in pollution-prone areas will also help bring down the cost.

For NPR News, I'm Scott Detrow in Harrisburg, Pennsylvania.