Lyft wants you to ditch your car. Not permanently, of course, but just for a few weeks.

Their new Ditch Your Car program, announced today, offers more than $400 of transportation credit to a group of Pittsburghers who will give up their cars for 30 days (Oct. 8 through Nov. 6). Instead of filling your gas tank and driving your own car, the program suggests getting around town via Lyft rides, Zipcar and Pittsburgh Bike Share’s Healthy Ride.

Here’s how it works: Pittsburghers can sign up here to enter, and 50 people will be randomly selected from that group. They will receive an e-mail with the details of the program, including transportation credits from Lyft, Healthy Ride and Zipcar to get around the city for one month (and, presumably, some details on how they’ll know whether you drove your car or not).

Although we can’t quite imagine not driving for a month, this promotional gambit got us thinking: What would it be like to stop gassing up our cars and leave them home for a month? How much might that save the average Pittsburgher?

The answer to that last question varies depending on how much you drive and also where you live: Our reporting found that if you fill up your tank at Marathon Gas on the corner of Penn Avenue and 40th Street, it will cost you $3.13 per gallon. But drive just another five blocks south to the BP at the corner of 40th and Liberty Avenue, and it would cost $3.17.

We asked a local expert to help us understand why.

Professor Eric Beckman is a co-founder of the Mascaro Center for Sustainable Innovation at the University of Pittsburgh, which focuses on designing green neighborhoods. He explained that the issue actually has very little to do with the gas itself.

“The price that these stations pay for gas to their wholesalers doesn’t vary too much, simply because there aren’t that many refineries in the U.S. anymore. So there isn’t a large variation in wholesale costs,” he explained in an e-mail to NEXTpittsburgh, “This leaves the economics of individual sellers.”

Though it sounds counterintuitive, not every gas station makes its profit from gas. As Beckman explained, some depend on selling snacks and groceries, while others get by on cigarettes and lottery tickets.

In addition, prices can vary depending on whether or not managers own or rent their respective gas stations, and how much those rents might be in a given neighborhood. All of these considerations influence the exact price of gas at each station. 

These factors have the effect of driving down the price of gas near popular destinations and more affluent neighborhoods while driving up the price of gas in the least affluent, more isolated corners of the city.

According to GasBuddy.com, a driver leaving the Oakmont Country Club can pay $3.05 a gallon to fill up his tank, while the residents of Mt. Oliver pay $3.27.

If you normally fill your tank in a neighborhood where gas costs more, perhaps ditching your car — or simply hunting for gas in a different location — might be a money saver worth considering.