By Dan McLean, Free Press Staff Writer

Vermonters can be thankful for plummeting gas prices as they pack bags for Thanksgiving travel, but motorists might want to wait until they cross the state line — or at least get to Rutland — before filling up the tank.

Vermont had the fourth-most expensive gas in the country Tuesday, 23 cents more than the national average for a gallon of regular unleaded, according to AAA data. The only places with more expensive gas in the U.S. were Alaska, Hawaii, New York and Washington, D.C.

Historically, Vermont has tracked closely to the national average. Two months ago, the state boasted some of the lowest gas prices in the country, according to AAA.

Local price margins might be part of the reason gas costs more here. Burlington area gas station are marking up gasoline 17 cents per gallon more than the national average, according to data supplied by the American Petroleum Institute.

"My office is investigating this very issue," said Sen. Bernie Sanders, I-Vt. "I think this is an issue where we need some federal intervention to find out what is going on. We want to find out if there is any restraint on trade here, if there is any collusion.

"We think there is a lot of secrecy in the price structure" of gasoline, he said, adding filling stations are charged different prices through practice known as "price zoning."

Joseph Choquette, a lobbyist for the Vermont Petroleum Association, said each gas station sets its own price.

"I think we have a very competitive market out there," Choquette said. "Senator Sanders is sitting in Washington and sees the world as a major oil company. We don't have any major oil companies in the state of Vermont."

Gas could be found for less than $2 a gallon in 36 states Tuesday. The average price of a gallon of regular unleaded in Vermont was $2.12, according to AAA. That's down 48 percent from the record high statewide average of $4.09 set in late June. Despite the price drop, Vermonters pay 12 percent more than the $1.89 national average for regular unleaded.

The Burlington-area price was a few cents higher, $2.18 a gallon. Better deals can be found outside Chittenden County.

Saratoga Springs, N.Y.-based Stewart's Shops, for example, sells regular unleaded for an average of $1.93 a gallon at its 10 stations in southern Vermont, including Rutland County, said Tom Mailey, the company's marketing director.

Tom Williams, the Vermont manager for AAA Northern New England, continues to be puzzled by the gas prices disparities.

On Oct. 1, the statewide average for regular unleaded in Vermont was 6 cents less than the $3.61 national average. One month later, the Vermont average was 29 cents more than $2.46 national average, Williams said.

"Prices are coming down. ... The station owner sets the price, and they have been discounting or cutting their price less rapidly than those in other areas of the country. That's clear," Choquette said.

John Felmy, chief economist of the Washington, D.C.-based American Petroleum Institute, said the price fluctuations are likely explained by "local supply and demand conditions."

The higher price can't be pinned on taxes. Gas taxes in Vermont are 38 cents per gallon, including state and federal taxes —10 cents less than the national average, Felmy said.

What is not less than average, however, is the gross profit margin on every gallon, or the amount filling stations mark up the price, Felmy said. In addition to taxes, the stations in the Burlington area add 46 cents to the wholesale price for one gallon, which is $1.36, Felmy said, citing data from the Lundberg Survey.

The national average, however, is a markup of 29 cents per gallon, he said, noting Boston stations add 19 cents and those in Portland, Maine, add 20 cents.

Historically, the gross profit margin is about 9 to 10 cents a gallon, he said. Felmy said he did not know why the margin was higher in Burlington.

"Vermont is at the end of the supply chain," and Vermont gas stations sell a fraction of the national average, Felmy said.

Sanders said he is going to ask for the cooperation of federal agencies to assist in investigating the price structure of gas. "I don't want to see the people of Vermont being ripped off," he said.