On an Island already known for its high cost of living, the Vineyard now claims the dubious distinction of having the highest gasoline prices in the state and among the highest in the nation. Prices for regular gas eclipsed the $4 a gallon mark at most Island service stations this week, while premium prices climbed as high as $4.39 a gallon.

On Wednesday, regular gas at Airport Mobil was selling for $3.98 a gallon, while a gallon of regular at Menemsha Texaco was selling for $3.75. A gallon of regular at the Citgo station and the Tisbury Shell station in Vineyard Haven cost $4.19 while regular was selling for $4.05 a gallon at Edgartown Depot and $4.09 a gallon at Edgartown Mobil.

Prices for premium gas ranged between 25 and 40 cents more than regular gasoline.

By all accounts, these prices are an all-time high, as the national average price of gas surged 22 per cent over a year ago. Diesel fuel prices reached a national record of $4.20 a gallon earlier this week, while crude oil peaked at $117.48 a barrel on Monday, up 79 cents, also a new high.

One motorist filling up the tank of her 2004 Honda Accord stared in disbelief as the meter eclipsed the $50 mark and headed for $60. “It’s not like I’m driving a Land Rover or a [Cadillac] Escalade, this is a small sedan . . . it’s enough to make you cry,” she said.

Data gathered from the American Automobile Association indicated the national average for a gallon of regular unleaded gasoline was $3.55 — which represented an all-time high for domestic gas prices. Information from the U.S. Department of Energy Web site indicated that motorists in Dukes County are paying more for gas than almost all drivers in the nation, excepting a few counties in California, the state historically with the highest fuel costs.

A quick survey of off-Island gas stations in the region shows motorists here are paying approximately 50 cents more a gallon for regular gas. The Palmer avenue Texaco Station in Falmouth was selling regular for $3.47 a gallon on Tuesday, while the Ashley Boulevard Mobil Station in New Bedford was selling regular for $3.49 a gallon.

Several gas stations in the metropolitan Boston area were selling regular for around $3.50 a gallon.

And while Vineyarders are accustomed to paying extra for everything from home insurance to a gallon of milk, as gas prices broke the $4 mark this week, well before the start of summer, it was especially disheartening.

Normally, gas prices on the Vineyard peak during the summer months when motorists drive more and demand is highest. Now many believe the stage may be set for gasoline to sell for $5 a gallon or more by July or August.

“It’s really scary,” said Michael Rotondo, the owner of Airport Mobil. “At this point I don’t think it’s a question of if we will see $5 gallon, but when. It wouldn’t surprise me if it happened this summer.”

Mr. Rotondo said a big factor in the trend of increasing gas prices is the change in demand in the Asian market, most notably the recent emergence of China as one of the world’s largest consumers of crude oil and gasoline. “They’re taking fuel wherever they can get it, and it’s putting a drain on the rest of the world,” he said.

Mr. Rotondo said that because the Vineyard is at the end of the supply chain, it faces additional costs. He noted that his supplier recently added a fuel surcharge for delivering to the Island, which was in addition to the hourly rate he already pays for the truck and driver to come to the Island.

Mr. Rotondo said he actually makes less money when gas prices increase because he has to pay more for each gallon, and more people charge gas to their credit cards. The station pays the credit card company between 1.5 to 3.2 per cent for every transaction. He said he often absorbs seven or eights cents for each gallon he sells to try to keep gasoline affordable to consumers.

But despite this, many motorists look at what they pay for gas off-Island compared to what they pay here and automatically blame the service station owners, he said.

“I know our employees hear the grumbling and the complaints, and I hear them too. People think they are getting ripped off. But if I had my way I would go back to the days of $1.69 a gallon for [regular] gas; it was better for everyone,” Mr. Rotondo said.

Ralph Packer, owner of R.M. Packer Co., which supplies the Island Shell stations, also said he has heard gripes about high gas prices on the Vineyard recently, but he too said he does not have as much control over prices as many people think. He said the petroleum industry has always worked on a system of profit margins, as opposed to retailers who keep to a fixed profit percentage, regardless of base price increases.

Mr. Packer said gas stations earn a certain number of cents per gallon, regardless of the price. Even if the price of gas goes up, the percentage stays the same, he said. Mr. Packer’s 30-year-old company is headquartered in Vineyard Haven, and is both a wholesaler and retailer of gasoline. Mr. Packer also operates a marine transport facility for petroleum products. The company ships some four to five million gallons of gasoline to the Vineyard every year.

Mr. Packer said he has also been hit by fuel surcharges, and has been forced to shift some of that cost onto consumers. But overall, he said, people have been understanding about the steadily increasing gas prices.

“I think the issue being in the newspaper and on the nightly news has helped people to understand the reality of the situation. People understand this is a worldwide trend and not a Vineyard trend,” he said.

Although he is in the business of selling diesel, heating oil and gasoline, Mr. Packer said he supports renewable energy and conservation.

“I just read this report that found that only one in ten pickup trucks on our nations’ roads are carrying any type of load, and only one in 20 sports utility vehicles is actually used for rough terrain . . . maybe a four-dollar or five-dollar gallon of gas will get people to start thinking about conservation,” he said.

Many Island officials this week said people may already be responding to escalating gasoline prices.

Angela Grant, Martha’s Vineyard Transit Authority administrator, said there are some signs that high gas prices may be boosting ridership. The number of passengers on Vineyard transit busses through the end of March was 768,873 compared to 685,882 through the same period last year. Although Ms. Grant said it is hard to directly link the two, she conceded there was likely some correlation.

“I think it’s a combination of people wanting to save money on fuel and also help the environment. We know people are attached to their cars, but when you’re talking about $5 for a gallon of gas I think it’s natural for people to start thinking about other [modes of transport] like the transit authority,” she said.

Paul Pimentel, an Edgartown resident and professional engineer with 40 years’ experience in energy efficiency and renewable systems, agreed rising fuel costs may force people to start thinking differently about energy consumption and alternative energy. But he also warned that sudden shifts in the market can have a devastating effect on the people who can least afford it.

“I think in the lon run, these market trends will begin to shape the way people think about conservation and renewable energy. But when these changes happen so rapidly — as they have in recent months and weeks — they tend to affect people living on a basic subsistence level in very hurtful ways . . . it’s symptomatic of our culture and our dependency of these energy sources,” he said.

And all around the Vineyard this week, there were signs that the crush of gas prices may begin to hurt people in a real way in the coming months. Elza Minor, a taxi driver for Adam Cab who has worked on the Island for several years, seemed to sum up the sentiments of all Vineyard motorists when he remarked: “It’s already tough enough trying to make a living — and $4 a gallon is rough — but what can you do? You just hope the prices level off and don’t go up.”