I like the https://www.fuelly.com https://www.fuelly.com web site to see what other people are getting as well as trend lines. For example - https://www.fuelly.

I like the https://www.fuelly.com https://www.fuelly.com web site to see what other people are getting as well as trend lines. For example - https://www.fuelly.com/car/toyota/prius/2021 https://www.fuelly.com/car/toyota/prius/2021 In my area there are 2 types of gas stations - ones with Ethanol and ones that target motorcycle advertising "100% gas" which is more expensive, but you definitely get more MPG. If I were you I'd try a different brand for a few fill ups and chart the differences.