Apr. 25—For a while Thursday, the Xpress Fuel station at 338 Route 12 in Groton had some of the cheapest gas around.

When a reporter pulled into the station at 2:30 p.m., Xpress was selling the stuff for $3.39 a gallon, 30 cents less than the daily average in the New London-Norwich metropolitan area, according to AAA.

By the time the reporter returned 15 minutes later, the price had climbed to $3.49, putting it on a par with the price being charged at the Route 12 Citgo station about a quarter mile away and by the Costco off Interstate 95 in East Lyme.

A random check of prices in the area found they ranged at least as high as $3.85, the credit price charged at the Citgo station on Williams Street in New London's Hodges Square. In the New London-Norwich area, Thursday's average price of $3.69 was up 10 cents in the previous week and 29 cents in the previous month. The price a year ago was $3.60.

"Lower demand and a drop in oil prices could push pump prices lower," Tracy Noble, a spokeswoman for AAA Club Alliance in Hartford, said.

"Domestic gas demand is pretty pokey at the moment, which is often the case in the run-up to Memorial Day and the traditional start of summer driving season," Noble said. "The recent national average price of $3.67 could be the peak until hurricane season is well underway. But as always, the wild card will be the cost of oil, so stay tuned."

Thursday's national average gas price was $3.65, 12 cents more than a month ago and the same as a year ago. Connecticut's statewide average was $3.72, up 10 cents in the previous week and 12 cents higher than a year ago.

At the Sunoco station on Williams Street in Hodges Square, where the price was $3.79, a manager who declined to give his name wanted it known that "the company" sets the gas prices.

"I want to put it at two dollars," he said, smiling.

Next door, at the Citgo station with the $3.85 credit price ($3.75 cash), the owner, Moe Ray, of Glastonbury, spoke by phone.

"It's the transition from winter blend to summer blend," he said, offering another explanation for the recent spike in gas prices. "In New England, we have this change in blends. The price started climbing last week. It will start going down gradually ― maximum two more weeks of high prices."

"Every station has its own circumstances," he said, addressing the variation in prices from station to station. "What gas costs depends on (the station owner's) contract.

Branded stations ― the Mobils, Shells, Citgos and Sunocos of the world ― tend to charge higher prices than unbranded ones, he said, partly because their higher-quality gas contains additives the others' don't. The distance gas travels before being delivered to a station also affects the retail price, he said.