Does auto-disabling WiFi based on GPS fences save battery life? I came across an IFTTT recipe that auto-disables WiFi on android when leaving a geographic area. The idea being that it save battery life since it wouldn't try to use WiFi elsewhere. 

Does this idea make sense? Or would GPS probing waste more battery life?
Your question boils down to battery savings WiFi Vs GPS for which I am not aware of a definitive answer


I am not familiar with IFTTT, but check if location update rate is possible to be varied
Macrodroid another easy to learn automation app allows you to configure update rate, so that you can vary updates to optimise on battery





Alternatively, if you are using GPS only for geo fencing, it  would be better to use cell tower groups to use as a trigger for switching on/ off Wifi - another feature of Macrodroid