TIJUANA, Mexico (CNN) -- More Americans, tired of skyrocketing gas prices, are crossing the border to Mexico, where fueling up costs a great deal less.
But the AAA Auto Club warns the short-term savings could spiral into long-term expenses.
Right now a gallon of gas costs about $3.10 in Tijuana, while it's about $4.60 just north of the border in the United States.
That's a $30 savings on a 20-gallon fill-up.
It makes financial sense to commuter Ricardo Fernandez, who lives a few miles away in San Isidro, California. He makes the international run once a week during off hours and doesn't mind waiting in line -- both coming and going.
"Right now the traffic is not bad to go back," Fernandez said. "It takes me about an hour, hour and a half."
While it sounds like a big hassle, Fernandez said he just makes a shopping day out of it.
"I can come shopping ... get some groceries and stuff like that," he said. "It's like saving double." Watch Americans buying gas in Mexico »
The story is a similar one for Pedro Hernandez who lives in Santa Ana, California, about 100 miles to the north. He doesn't make a special trip just to gas up, but he won't pass up a deal either.
"We can come down to visit relatives and shop around," he said. "While we're here, might as well fill up the gas."
Hernandez saved about $40 on his tank.
But the savings might come at a cost: Mexican gas is made with a different formula -- containing more sulfur -- which could hurt your car in the long run, according to Stephen Mazor with AAA's Automotive Research Center.
That fuel mixture can ruin the emission control equipment on American cars and cause them to fail emissions tests.
"Then (you) have to spend a lot of money to repair your car because of the effects of that gas," he said.
Fernandez said his truck is running fine on the Mexican gas, for now, which is all he can afford to worry about until U.S. gas prices go down.