Hi Dick,
Great question. The Fuel database is included updated anytime you do a Weather/TFR update, so if using iFly Connect or the Update Package process, just check that option and you are good to go.
If you are connected to a WiFi network with your 720 (if using our app on a tablet, this applies to you too) - Weather, TFRs, and Fuel data is automatically updated periodically in the background, no need to do anything. But you can also select the "Weather/TFR" option on the 720's WiFi update mode to force the Fuel database to be updated.
Thanks!
Walter