CHICAGO (CBS) — Seven cents in just one week. That’s how much gas prices in Chicago have jumped on average, according to

Motorists are spending an average of $4.25 a gallon to fill up. But there’s more to the jump than you might think, CBS 2’s Mai Martinez reports.

Seventeen different territories are required by the EPA to have special blends of gas to meet air-pollution standards. Most of Illinois and Indiana can use just regular unleaded gas.

A sliver of downstate uses one blend; Minnesota another; California two more blends. Chicago has one, too, and that’s part of the reason we’re paying more at the pump. But that’s not all.

Everyone knows the prices are going up, but they’re not exactly sure why.

Patrick DeHaan, senior petroleum analyst at, says the reasons are many.

“The reason why Chicago tends to be toward the higher side is that Illinois has one of the higher tax rates in the nation,” he says.

DeHaan says doing business in Chicago also just costs more, so gas stations pass that along to customers. It doesn’t help that a major refinery in Northwest Indiana is partially closed for maintenance.

“That is keeping supply tight, and that’s also pushing gasoline prices up as well,” he says.

As for that special type of gas required in Chicago, most drivers said they had no idea.

“Who came up with this plan in the first place? I mean, it sounds kind of exploitive to me,” driver Donna Rose said.

Some members of Congress, including U.S. Sen. Mark Kirk, also feel the 17 gas “monopolies,” as they call them, are unfair.

Kirk is calling for one type of clean-burning gasoline for the entire country.  Kirk feels leveling the playing field will increase competition and lower gas prices.

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