having bought mine in March when should I expect it to enter FMM? should I start trying to burn some off now? I don't mind the idea of burning gas on the way into work as it can cool down in the parking deck but really prefer to come home pure EV as it doesn't heat up my garage
The Fuel Maintenance Mode (FMM) occurs when the computer determines the "average age" of the gas in the tank is ~12 months old. If you bought a brand new Volt in March and if the dealer filled the gas tank for the first time just before you bought it, the gas in your tank is now ~5 months old. The FMM won’t happen for another ~7 months.
If you bought a used Volt, or if the gas had been put into the tank long before you bought it (did the dealer "top off the gas tank" for you, adding fresh to existing gas, or was the tank less than full as you drove it home?), there’s really no way to determine how much beyond ~5 months the current "average age" is.
What is true, though, is that if you’re not using gas fast enough to contemplate getting more gas within the next 7 months, then contemplate ways to use up your existing gas... using the current gas range estimate (which is probably low), how many gas miles would you need to drive per week (or work day or whatever) to use up the existing gas within, say, 6 months? Or would you rather just use battery now, and let all the gas miles happen when they happen?
Or, take a long drive in Hold mode in a couple of weeks to view the eclipse... drive to work in Hold to see how it feels to drive with the gas engine running... Winter season is coming in a couple of months, where you can heat the cabin by running the ICE...