Yesterday's Prices

Noted yesterday, as I was driving around doing some errands:

• Gas was priced at $2.649 a gallon in my town, which is on the outskirts of the metropolitan Indianapolis area.
• But gas was priced at $2.619 on the far northeast side of Indianapolis.

I don't know why there was a discrepancy and especially why gas was priced cheaper in the city than in the country.