I find that I can use Gas Buddy to check prices in other towns. When traveling, I work out when and where I will be refueling and check prices in that town, a few towns prior and post stopping. Generally this works pretty well. Typically I get fuel from Sam's since I park overnight in their lots. It's more convenient to top off fuel when stopping overnight rather than waiting until I need to refuel or run out of fuel. Unfortunately, Sam's does not always have diesel, so I need to look around a bit for diesel. For the bus, I can skip a night of refueling if need be. I have created a POI list of Sam's clubs and note on them if they have diesel (G/D) or just gas (G) along with if overnight stays allowed (usually yes). The Gas Buddy app allows me to see where the best price for fuel is in almost any town. It would be nice if more people would update the prices. I only believe prices that have been updated less than 12 hours ago.
As of this morning (when we got gas for my Jeep) our local prices for Sam's Club (NM) were:
Reg $3.059
Prem $3.659
Diesel $3.659
Sam's club is the lowest price in town today for both gas and diesel.
In Lubbock TX (170 miles away and in another state), Sam's Club prices for today are:
Reg $2.799
Prem $3.199
Diesel $2.959
In Brownfield, TX (130 miles away and in another state), The Valero is the cheapest in that town as of a few minutes ago:
Reg $3.129
Prem $3.899
Diesel $3.449
I just checked prices without ever leaving.