K., Bom Dia. I suppose where you are is effectively "south of Boston".
Since most of my trips are well within the battery range, the on-board generator is used infrequently. GM considered this and uses an "Engine Maintenance Mode" function that starts the engine every few months to keep things lubricated. There's also a "Fuel Maintenance Mode" to calculate the average age of the fuel in the tank to avoid stale fuel. I've found that leaving just a gallon or so in the tank is enough to avoid the low fuel level warning, avoids the EMM, and means less fresh fuel needs to be added every few months to update the average age and avoid that alert message.
Between these mandated gasoline usage programs, and the few trips I make beyond the battery range, I've used 183 gallons in 58 months of ownership (about 1.25 gallons per week).
Grid electric cost per mile: $0.022
Gasoline generated electric cost per mile: $0.079 per mile.
Yeah, I plug in to recharge as much as I can.