Brent Saba had just dropped a church group off at Philadelphia International Airport on Sunday morning and was heading north on Interstate 95 when his 15-passenger van ran out of gas.

Saba, a 24-year-old church pastor, made it to the shoulder and waited more than 30 minutes for someone to stop and lend him a cell phone. Then he waited a while longer for AAA to arrive with fuel.

With gas prices hovering at $4 a gallon, motorists like Saba are putting less fuel in their tanks — then coming up empty on the highway.

Though national statistics on out-of-gas motorists don’t exist, there’s plenty of anecdotal evidence that drivers unwilling or unable to fill ‘er up are gambling by keeping their tanks extremely low on fuel.

In the Philadelphia area, where the average price for a gallon of regular broke $4 Friday, calls from out-of-gas AAA members doubled between May 2007 and May 2008, from 81 to 161, the auto club reported.

“Some of them are embarrassed. … They say, ‘I was trying to make it till Friday,’ and they couldn’t do it,” said Gary Siley, an AAA mobile technician who has assisted numerous out-of-gas motorists.

Research from The Nielsen Co. shows that drivers have been making more frequent trips to the pump but limiting how much they put in the tank.

Convenience stores, which sell about 80 percent of the nation’s gas, are seeing fewer fill-ups, said industry spokesman Jeff Lenard.

“When the pump hits a certain dollar amount now, you’re seeing more customers stop,” said Lenard, with the National Association of Convenience Stores. “They’re purchasing fewer gallons.”

And that means playing Russian roulette with the gas gauge.

In Dallas, Courtesy Patrol — a roadside assistance program operated by the sheriff’s department — reports a doubling in the number of daily fuel calls from stranded motorists in recent months. Sheriff Lupe Valdez herself recently came to the aid of a mother and her two children who had run out of gas along an interstate.

In some cases, motorists have gotten stuck in the middle of the highway, creating a dangerous situation, said Lonnie Lankford, a Courtesy Patrol shift leader. “It’s just breaking the backs of the people, these gas prices,” he said.

Transportation officials in Oregon and Tennessee also report increasing numbers of stranded motorists in need of gas.

AAA Mid-Atlantic, which has nearly 4 million members in Delaware, Maryland, New Jersey, Pennsylvania, Virginia and the District of Columbia, reported a 15 percent year-over-year increase in calls from members with empty tanks.

“We’re seeing a lot of frustrated motorists who are trying to cut corners, and this is one way they’re doing it,” said AAA Mid-Atlantic spokeswoman Catherine Rossi. “But they’re shooting themselves in the foot, or the wallet, in the long run.”

That’s because perpetually running on fumes can damage a car’s fuel pump, requiring repairs that make a full tank of $4 gas seem like a bargain.