By ABC-7 Reporter Martin Bartlett

CIUDAD JUAREZ, Chihuahua -- While consumers just across the Rio Grande in El Paso are paying about $4 a gallon for gas -- more for diesel -- government subsidies here have kept fuel prices well below the $3 per gallon mark.

Those low prices have kept El Pasoans hopping the border to stay ahead of sky-rocketing fuel prices at home in the United States, many of them filling up portable tanks with diesel which sell for between $300 and $1,000 in El Paso.

"Over the past three months with the price of diesel up where it is, we've seen an incredible increase in people buying them so they can buy diesel in Juarez," said Dick Krasne, president of Alamo Auto Supply on I-10 near Geronimo Drive in Central El Paso.

"The word has gotten out and people are asking for them specifically for that," he said.

The cross-border commerce is raising the ire of some Mexican fuel consumers in Juarez; they don't like the idea of U.S. consumers taking advantage of fuel prices kept artificially low courtesy of their own tax dollars.

Dr. Tony Payan, political science professor at the University of Texas at El Paso, said it's more likely, though, that the spiking number of U.S. citizens buying fuel in Mexico are actually lining the pockets of oil giants in Houston and Dallas rather than the government-owned PEMEX oil company in Mexico City.

Because of a lack of refining capacity in Mexico, Payan said many oil fields in northwest Mexico export much of their crude oil to refiners in Texas, who in turn send refined gas and diesel back to Mexico for sale at stations along the border.

Refining profits and jobs stay behind, though, north of the border in Texas.

Officials at Western Refining in El Paso say they sell gas and diesel to distributors in Mexico but do not import crude from Mexico.

While there are no firm number for the impact on the Texas economy, Payan estimated it in the billions.

"Texas benefits enormously from this," he said.

It is legal to bring gas and diesel back from Mexico.

But if customs agents think you're bringing back too much to use yourself, they'll turn you back or send you to a cargo facility to cross it there.

"There have been mixed stories about how they're enforcing it, it's very unclear to us," Krasne said of customers who've bought the tanks to transport fuel across the border.

However, if gas and diesel prices start to climb again, customs agents will likely see more fuel-toting border crossers -- and that's clear on both sides of the border.