If you hop from gas station to gas station, you've undoubtedly noticed that gas prices can vary widely — even at stations that are in close proximity to each other.
Boston University professor Robert Kaufmann, who studies world oil markets, says drivers tend not to notice these price differences until gas prices skyrocket, and then drivers suddenly pay much more attention.
"There's wide variation in prices among gas stations," he said. "It's something that most of us, unless you're cheap like me, don't notice most of the time."
He says an essential element is if a gas station has a convenience store and more foot traffic.
"When you fill up, you go in, you buy a soda, you buy a treat, and for those gas stations they make a lot of their money selling you these treats," he said. "So they're going to try and keep prices low because they want you coming into the station."
Other factors can include how much the gas station paid for gas, how much it pays in property taxes, and its distance from the highway.
"The first station that you see on your side of the road will have the highest price, and if you drive down the road a half mile, a mile, you find oftentimes a much lower price just because there's less traffic to those distant stations," said Kaufmann.