That's an extreme case though, and not what this sort of thing is aimed at.

Here in Perth, Western Australia, it's common for pump prices to vary significantly even within a small radius. But they're all on https://www.fuelwatch.wa.gov.au/ so you can see what the price is ahead of time.

If it's 14c cheaper per litre (coming up for 10%) to go 500m one direction vs 500m another direction, which one are you going to choose?