All of these apps are free, and they all work with bothAndroidandiOS.
Best for Finding Stations on Road Trips: Gas Buddy
Automatically show cheap gas along your route.
Identifies good places to stop based on gas prices.

Payment feature can save you some money too.
Advanced trip planner is only on the website.
Gathers lots of private data.

Gas Buddy is a feature-rich gas app, but its route feature is indispensable when planning a road trip.
You probably already have it.
Excellent for creating routes and navigation.

No advanced sorting features.
Wont show stations out of your area unless you run a new search.
This automatically brings up a map of the closest gas stations along with prices.

Best for Cash Back: Upside
Provides money back within days.
Receive funds via PayPal, check, or gift card.
Sometimes has cash back offers for restaurants and groceries.

Only shows gas prices for participating stations.
You have to pay full price then wait to be reimbursed.
Best for Contactless Payment: Waze
Automatically alerts you when contactless payment is available.
Launches the right app for your location.
Works with multiple gas station chains.
Payment isnt handled in-app.
Requires the installation of additional apps.
It then gives you the option to launch the corresponding gas station app if you have it installed.
Best for Accurate Prices: Geico Mobile
Up to date gas prices from OPIS.
Dont need to have Geico to use it.
Lacks some advanced features.
Geico policyholders will get more utility out of it.
You dont need an account, and you dont need to have Geico insurance.