Motorists express dismay but not surprise at the pump. L.A. is not far behind at $3.878 a gallon.

SAN FRANCISCO, CA — Finally, it happened.

After days of inching upward, gasoline on Sunday crossed the $4 threshold in San Francisco. The city became the first in the mainland U.S. where the average gallon of regular unleaded self-serve gasoline cost more than $4, according to AAA’s Daily Fuel Gauge Report.

To be exact, the average in the city was $4.006.

People tanking up didn’t express shock. Some were angry, and some resolved that they would get used to the new normal. This being the sort of city that has a monthly bicycle rights protest, some were positively gleeful at the $4-plus price.

"I like it when it goes up," said Shannon Wu, 26, an events planner from Oakland who was filling up a Honda Element. She hired the vehicle for the day from a car-sharing service so she could help her boyfriend move. She hasn’t owned a car for a couple of years.

"Anything that discourages driving," she said, "is good."

Other California cities will probably soon see signs for $4 regular too. "San Francisco is just the suffering pioneer," said Judy Dugan, research director for Consumer Watchdog, a nonprofit consumer advocacy group. "The rest of California will soon follow, and most likely the rest of the country."

Many cities were a half-step or less behind on Sunday — with the average at $3.878 in Los Angeles, $3.994 in Santa Barbara and $3.924 in San Diego.

San Francisco wasn’t the first in the U.S. with an average above $4. Earlier this month, the island of Maui got that honor.

But with a new high price on the mainland, analysts expect energy to be the talk of the summer. Consumers will ruminate more on the implications of $4 gas than they did of, say, $3, a barrier broken in California in May 2006. (Gasoline crossed $2 a gallon in the state in September 2003.)

"Four dollars is truly a mental barrier for a lot of people," said Michael Geeser, a spokesman for AAA of Northern California. When it comes to actually filling their tanks, though, "for many people, it doesn’t matter if it’s $4 or $3.97. They still have to use their cars to pick their kids up from school or get to work."

Nationally, the average price was $3.508, a record, according to the Energy Department’s latest weekly survey.

Demand is expected to increase as summer travelers take to the road. If anything happens to pinch supply — a hurricane off the Gulf of Mexico, a workers’ strike on an oil field in the North Sea, political unrest in an oil-rich country — "it will be pretty easy to see a national average of $4," said Andrew Lipow, president of Lipow Oil Associates, a Texas-based oil consultant.

"I’m surprised the whole oil market has moved up so quickly," he said. "It has caught a lot of people off guard."

The first time the national average crested the $2 mark was in May 2004. It hit $3 in September 2005 in the wake of Hurricane Katrina. Prices in California are higher mostly because of the cleaner-burning gasoline the state mandates.

At the Shell station on the corner of Folsom and 5th streets, where regular unleaded cost $4.199, there was little talk about blame. As they watched the numbers ratchet up like on a casino slot machine, some motorists talked about survival strategies.

Eric Miller, 27, bought just one gallon of regular unleaded for his Saturn so he could get to church. "I can’t afford gas right now," said the Daly City resident, who does several odd jobs to get by. "You have to buy a gallon at a time."

Likewise, a man who gave his name as V. James put just $5 in his Toyota Celica so he could get over the bridge into Berkeley to meet friends. He would fill up there, he said, where he believed gas was cheaper. "We can bang our heads against the wall, but it’s the new reality," said James, 60, who works at a BMW repair shop. "It means people will be more inclined to knock on the boss’ door to ask for a raise."

Mia Brumfield, 27, a campaign reports specialist from Sacramento who was visiting family and friends in San Francisco, said she joined a recent protest at the state Capitol over the rising cost of living. "Going to work now is what I can afford," she said. "I am angry but I don’t see a change."

In the Chicago area, unleaded sells for about $3.50, said Tom Brantner, who was ending a vacation with his wife in San Francisco and filling up his rental car. It’s not $4, but it’s a lot more than it was a year ago, and it’s having an effect.

"I see it at our church, I see it in our stores," said Brantner, 54, who lives in Algonquin, Ill., and is a salesman for a ball-bearing importer. "I think it’s really going to affect our country, and it scares me."

Contact the author at [email protected]