Greg Beato synthesizes why driving 10 minutes out of your way to save three cents per gallon on gas isn't worth it:
A 10-minute detour theoretically results in a 20-minute round trip. At an average speed of 45 mph, the trip would cover 15 miles. If your car gets 30 miles to the gallon, you have to burn half a gallon of gas to reach the station with the cheaper prices. At $4 a gallon, that’s a cost of $2. To make such a trip worth your while (without factoring in the value of your time or the additional wear and tear on your vehicle), you’d need a fuel tank capable of holding 67 gallons. At a savings of three cents a gallon, that 67-gallon tank would cost $2.01 less to fill up at the cheap station versus the more expensive station. This means that after subtracting the cost of the extra fuel it necessitations, your excursion would save you a penny!
The Dish 