[sloped]

Track it! Any Spreadsheet. Columns: date, where you filled up, how many gallons, dollar total, odometer reading, mpg function ((currentodo - prevodo) /gallons), ppg function (total / gallons).

You could also install something like https://lubelogger.com/ (naming decision aside), if you happen to do any self-hosting. It is a lightweight vehicle tracker. It has a fuel tracking screen. I personally only use it to track maintenance, but have been thinking about starting to track fuel consumption given the current disruption.