Say you woke up yesterday morning in Philadelphia and wanted to get as far away from there as you could by the end of the day. You decided to head west on Interstate 76, so you filled up your the tank of your car. Your price per gallon for regular unleaded: $1.74.

In Harrisburg, you pull off to refuel both body and vehicle, and find that gasoline there is $1.66 per gallon, a price that makes you disregard the sign on the pump that says, "Do not top off." You want every drop of $1.66 you can get.

By dinnertime, you're in Pittsburgh. You find a klatch of service stations and -- yikes. They're all charging $1.78 a gallon.

Welcome to the arcane and convoluted world of gasoline pricing. Why, as one moves across the map, are gasoline prices all over the map?

Location is a factor, in more ways than one.

"Certain places are farther away from terminals, and that could impact the price," said Jeff Lenard of the National Association of Convenience Stores, the trade association for owners of convenience stores that sell gasoline, which are the most common type of gas stations. The farther away a station is located from pipelines and terminals, the more expensive it is to have gasoline delivered to it.

In that regard, Pittsburgh is less fortunate than the Philadelphia area, which is home to two large refineries: Valero Energy has a refinery 15 miles south of Philadelphia in Paulsboro, N.J., and Sunoco has a refinery in Philadelphia that produces 300,000 barrels of gasoline a day. Pittsburgh is even less fortunate than Toledo, Ohio which also has a Sunoco refinery, giving northern Ohio consumers an edge when they need to refuel.

According to the U.S. Energy Information Administration, as of last month, distribution and marketing costs accounted for 25 cents of every dollar spent at the pump. Taxes accounted for 19 cents, and paying for crude oil took 60 cents. That adds up to $1.04. The remaining category, refining costs, totaled a negative four cents, meaning that refiners lost money.

Like distribution costs, the taxes paid for gasoline also vary by location. While the federal excise tax of 18.4 per gallon of gasoline is uniform throughout the country, states impose their own taxes that vary widely. Pennsylvania's fuel taxes, totaling 50.7 cents per gallon, are more than four cents higher than Ohio's, at 46.4 cents per gallon. They are also higher than the national average of 48.4 cents per gallon. At the same time, they are lower than the state taxes in West Virginia, 50.6 cents, and New York, 60.9 cents (yesterday, the average price in Erie was $1.72; in Buffalo, $1.94).

Besides state taxes, some municipalities impose their own fuel taxes.

Then there is the matter of wholesale pricing, or the amount that retailers pay for the gasoline.

A branded retailer, such as a BP station, may be able to purchase gasoline only from that brand supplier. That supplier may offer discounts to a retailer located in an area that is known to be competitive, while a station in a less competitive market would not receive that discount. And in the world of retail gasoline sales, the market can be surprisingly small in geographical size.

"For a corner gas station, you're looking at a radius for people who travel five minutes," Mr. Lenard said. If a consumer can find a cheaper price within a five-minute drive of a location, they'll take it.

"There may be two identical brands within a mile of each other that may be dramatically different in price," he said. "It could be because the wholesale price was dramatically different in those two areas."

Finally, he said, differences between individual retailers may be partly a matter of pricing strategy. While one retailer may choose to keep prices as low as possible and make money on volume, another may opt to maintain a more constant margin and settle for a smaller number of customers.

He cited big-box discounter Costco as an example of the former approach: "Their strategy is, 'Come out for the gas, then go inside and buy a big-screen plasma TV.'"

Local market leader Sheetz, he said, is a good example of the latter strategy, whose "strong sandwich program" enables to them to operate as "a restaurant that happens to sell gas rather than a gas station that happens to sell food."