Do you shop around when filling your car with petrol or diesel, or do you just fill your tank wherever is convenient not worrying about pump prices?
Back when I was doing silly annual mileages for work I was always on the lookout for the cheapest diesel I could find. It was in those days that I discovered the PetrolPrices.com price comparison web site which gathers data on fuel prices at individual service stations.
To get the best from the PetrolPrices.com web site you need to register for a free account which then allows you to search by location and fuel type within a range of distance settings. If you have an Apple iPhone or Android smartphone there is also a PetrolPrices app which as well as letting you find the petrol and diesel prices near your current location features a route planner which shows prices along your journey. The PetrolPrices app can be downloaded from the Google Play Store and the Apple App Store.