Image credit: Kevork Djansezian/Getty Images

When it comes to overpriced gas, the United States doesn't look all that "united."

In California, drivers are finding high gas prices - more than $4 a gallon - across the state, according to an informal survey by ABC News.

The most expensive gas reported in America - at $5.21 a gallon - was spotted at a Mobil station in the Los Angeles area.

In the Northeast, the average price for a gallon of gas was between $3.60 and $3.93.

While the rest of the country seemed to pay between $3.38 and $3.71, a few   states saw prices of $3.16 and even lower. Fort Collins, Colo., was home to the cheapest gas at a U Pump It station - $2.94 a gallon.

Although prices always vary from state to state, Tom Kloza, a chief oil analyst for the Oil Price Information Service, said the current situation was unique.

"Now, it's normal for California to separate itself from the rest of the country," he said. "But it's very abnormal to see such weak pricing inside the Heartland and to see the coasts with some of the extreme. I think that'll continue for a while."

He said the refineries on the U.S. coasts were buying expensive crude from Saudi Arabia and Nigeria while the inland states received the cheaper stuff from Canada and North Dakota.

And the price disparity isn't just apparent on the national level.

In Dallas, where DallasGasPrices.com said the average price of gas is $3.59 a gallon, just a few miles made the difference between a Shell station selling gas at $4.19 and a Sam's Club and Costco selling it for $3.39.

Kloza said the big-box stores were able to sell more cheaply for several reasons.

"It's not about making money necessarily on gasoline in the big-box clubs," he said. "It's about getting you inside to buy all their other merchandise in those clubs. Last year, we saw a couple of them actually increase their customer counts by as much as 16 percent with cheap gas."

Greg Laskoski of GasBuddy.com, which offers a free mobile app to help you find cheap gas in your area, offered these reasons for price differences in the same city:

Overhead: Some retailers own their property and others lease. They also have different wholesalers.

Delivery: The timing of the delivery has an impact because wholesale prices go up and down daily. Retailers also anticipate the higher price in delivery so they hike their prices to cover the higher cost they have to lay out.

Location: Depending on the county, taxes can be higher or lower.