Are you ready for $4-a-gallon gas again?

For the first time in three years, pump prices this year may reach the psychologically frightening $4 threshold, which is sure to change some drivers' habits.

Gas prices are already the highest they've been since 2008, and a growing number of energy analysts think they will keep rising until the current $3.45 a gallon in the South Bay seems cheap.

"Gasoline prices will breach $4 a gallon in San Jose at some point in April or May," predicted Patrick DeHaan, senior petroleum analyst at gasbuddy.com. "Diesel prices in California should easily breach $4 a gallon in the next two months."

A lot of drivers are stressed about current prices, let alone price hikes.

"When I look at the price per gallon, it looks bad and I worry about people who have to drive a lot and are low-income to start with," said Joy Davis, a 56-year-old officer manager from Castro Valley who paid $43.86 for her most recent fill-up for her Hyundai Sonata. "It's going to affect the price of food, too, and everything else."

Brian Milne, an energy analyst with commodity tracker Telvent DTN, said oil, gas and diesel will all move higher. Susanne Garfield of the California Energy Commission said the gas increases are driven by the price of crude oil. "Crude prices have been on the increase since last year," she said.

Crude slipped to $85 a barrel Friday, falling on the announcement that Egyptian President Hosni Mubarak had resigned. But that's still about $20 higher than this time last year. Each $1 increase in crude turns into a 2.5-cent hike at the local service station.

The national average for gas is $3.13 a gallon, and for diesel it's $3.52, up 50 and 68 cents from February 2010. The San Jose average of $3.45 for gas is 52 cents more than a year ago, while diesel, at $3.79, is a whopping 74 cents higher.

What's troubling is that demand is flat and supplies ample. Prices usually tumble this time of year before rising in the spring, as people tend to drive more in warmer weather and California's blend of summer fuel is more costly to produce.

But if the recent turmoil in the Middle East spreads, energy experts say all bets are off and motorists will likely be paying even more.

The U.S. Energy Department last week predicted that the national average will hit $3.24 a gallon this summer, and Bay Area prices usually are about 35 cents higher. But the federal forecast is often on the conservative side, and the agency warns that there is a 35 percent chance the national average could hit $3.50 a gallon and a 10 percent chance it could reach $4.

Translated for Californians: We could be approaching the $4 mark, and that has some drivers beginning to react.

Dan Moore of San Jose bought a bicycle in December, partly to commute and fight off the $50 cost of filling up his Mazda Six.

Jeff Fenton of Menlo Park is leaving his Infiniti, which requires premium gas -- $3.85 at his last fill-up -- at home when running short errands in favor of his Volvo.

"I try to combine multiple stops on one trip, or go where I can do a one-stop shop," said Fenton, 51. "Or ask myself whether a trip is really needed."

Khoa Quach and his wife began carpooling together when prices approached $4 a gallon three years ago. He drops his wife off at the Diridon Caltrain station and she rides the train to work in Palo Alto. He figures he's saving about $80 to $90 every two weeks in gas costs.

Chuck Brassfield, a Chevron dealer in San Jose, said it's not uncommon for customers to come inside and ask for $3 worth of fuel. That's it.

"That's less than one gallon," he said. "Obviously they are just trying to get to work. It breaks my heart to see people in this shape financially."

Contact Gary Richards at 408-920-5335.