Get the GASBUDDY App. Prices, locations, maps.
I don't use maps all that often, but when I do it's just so that I can track travel time, etc. not for routing per se.
As for the gas prices, I can only wager that you're not seeing gas prices because nobody has reported them. Maps gets a LOT of its information from WAZE, including gas prices, accidents, traffic, etc... Try an experiment and report back....
- Map a route that you normally take
- Stop on that route and report the gas prices through the WAZE app (sign in with your Google account) as often as you can
- Run Maps again the next day and I bet you that the prices will show up...
Gas Buddy has the same "problem" - if prices aren't reported by others, it just won't work.
Make sure you have the most current version, 9.16.2.
Also, it seems it doesn't list prices for ALL gas stations, so you might just be in an area where none of them include that:
"Not all stations have prices listed, but it's definitely a good start. This is probably the beginning of another integration with Waze, which already offers similar price tracking."
[Update: Also Added Gas Prices] Google Maps v9.16 Adds Search For Places Along Your Current Route For Quick Stops To Get Gas And Food [APK Download]
I use it. I see gas prices. I just used it on a trip of 1900 miles. I confess, I find GasBuddy to be more reliable, with many more stations reported and up to date. We use it on two Samsung phones, the S5 and S6 Active.
FYI Gas Buddy has been known recently to have an issue with location and use a lot of battery.