Aug. 31 (Bloomberg) -- The price of regular-grade gasoline soared as much as 50 cents a gallon overnight as Hurricane Katrina forced suppliers to ration the fuel sent to filling stations and convenience stores.

Refineries and pipelines shut down by Hurricane Katrina -- which roared through the Gulf of Mexico over the weekend before slamming Mississippi's coast two days ago -- remained down. Some wholesalers and refiners were restricting the amount of fuel retailers can buy.

Gasoline prices in Dayton, Ohio, and in parts of Michigan rose 50 cents last night to $3.09, according to Brad Proctor, founder of Gaspricewatch, which relies on volunteer price- spotters to track retail prices. Similar jumps in Ohio, Indiana, Kentucky, Illinois, Wisconsin and Minnesota occurred this morning, he said.

``I have never seen a 50-cent jump,'' he said in an interview. ``It's amazing. The reason prices are going up is to make us drive less. If we can cut back on our driving by 10 percent, the gasoline prices will ease up. The industry is forcing prices up high enough that shortages won't occur, because we'll change our behavior.''

The average nationwide pump price for regular-grade was $2.72 a gallon, as of 4 p.m. New York time, compared with $2.62 yesterday, according to Gaspricewatch. It was $2.75 a gallon on Gasbuddy.com, another Web site that relies on volunteers for its data, an increase from $2.60 yesterday.

At those prices, it would cost $61 to $62 to fill up the tank of a Ford Explorer, the most popular U.S. sport-utility vehicle.

$4 a Gallon

``We're going to be over $4 a gallon retail by the end of next week,'' said William Shireman, executive vice president of Gas City Ltd., a 50-station chain based in Frankfort, Illinois.

Katrina idled 10 percent of the nation's refining capacity during a time when supplies were already below normal. U.S. Energy Secretary Samuel Bodman said that the government approved one release of oil from the Strategic Petroleum Reserve and is reviewing other applications. The oil would still need to be refined into gasoline for consumer use.

``It might be past $3 a gallon by this weekend,'' said Susan Broughton, communications director of the Society of Independent Gasoline Marketers of America in Reston, Virginia. ``Even if the refineries are brought on line, which takes a while, they can't run without electricity, water or employees.''

Going Up

Gasoline futures, which reflect wholesale prices at the New York harbor, have risen 36 percent in the past three sessions, including 5.7 percent today.

``We're seeing gas prices going up all over the place,'' said Jason Toews, co-founder of Gasbuddy.com. ``It's really amazing how fast they've gone up.''

Michigan motorist Bill Hammill, 29, pulled into a BP gasoline station in the Detroit suburb of Harper Woods last night and found piece of paper taped to the pumps saying only premium was available.

``I got a couple of dollars worth, and some other people who didn't want to pay for the premium left,'' Hammill, of Eastpointe, said in an interview.

Hammill, who drives a Malibu, said he keeps his fill-ups to $5 of gas because the higher prices are cutting into his spending money.

Midwest, Mid-Atlantic

The highest price in the country for regular-grade gasoline was $3.88 a gallon at Death Valley, California, according to Gaspricewatch. The lowest was $2.36 at Louisville, Kentucky.

Gasbuddy.com showed similar prices, with the highest prices in California and the lowest state average in Louisiana at $2.513. Demand has dropped in Louisiana as residents have evacuated and work commutes and other travel have ground to a standstill.

``Other than the obliteration in the south, the two places that will probably be affected most are Midwest and mid- Atlantic,'' said Paul Fiore, executive vice president of the Service Station Dealers of American in Bowie, Maryland. ``That's where a good percentage of their supply comes from.''

``I am not doing as much anymore,'' said Lavonne Medrigal, 34, an advertising photo editor in Los Angeles, who drives a 2006 Toyota Celica. She was filling her tank at an Exxon station selling regular-grade gasoline for $2.99, up from $2.75 yesterday. ``I tend to stay at home and make my boyfriend drive more. I have to budget everything now with gas prices that high.''

Cutbacks

In Boston, taxi driver Bahman Mahmoudi, 50, said gasoline prices at his favorite -- usually inexpensive -- service station in Brighton, Massachusetts, rose from $2.54 on Aug. 29 to $2.65 yesterday morning. It climbed to $2.72 by yesterday afternoon and $2.99 this morning.

``It's killing me,'' he said in an interview. ``Every day, it's so expensive. I tried to cut down other expenses -- food, clothing, everything.''

New Yorker Amari Concepcion, 30, said she's turning to public transport.

``I won't usually get a full tank,'' said while fueling her maroon Mercedes Benz. ``I've started putting in like $10 or $15. If I'm going to go certain places I can get by train, I'll go that way.''

Refineries Shut

Katrina forced the closure of eight refineries in Louisiana and Mississippi over the weekend. Some have yet to restore power or may be flooded and won't resume operations for as long as two weeks, refiners and analysts have said.

Colonial Pipeline Co., which runs the world's biggest network of petroleum-product pipelines, shut down two pipelines on Aug. 29. The 5,519 pipeline network stretches from Houston to New York Harbor, making it a primary artery for the Northeast. Spokesman Steve Baker said the company will bring in diesel generators this weekend to provide power to run the pipelines.

``I would hope that all consumers recognize the really catastrophic event that occurred with Hurricane Katrina,'' said Dan Gilligan, president of the Petroleum Marketers Association of America, in an interview yesterday. The Arlington, Virginia-based group represents about 8,000 marketers across the U.S.

``If consumers want to help, they need to find a way to conserve if they can,'' he said. ``Find a way to carpool for the next couple of weeks. If everyone would just decide to conserve a little bit, I think the industry can cope. If people are going way for Labor Day, maybe try to cut back the travel by 100 miles.''

Without a change in the supply-demand dynamic, Gaspricewatch's Proctor predicted the average U.S. price at the pump will rise 12 cents today to $2.84 by the end of the day.

To contact the reporter on this story: Margot Habiby in Dallas at mhabiby@bloomberg.net.

Last Updated: August 31, 2005 17:10 EDT