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I run almost exclusively in electric-only mode. The gas in my tank has been there for at least six months if not more. How long can I let it sit there before it "goes bad"? Should I put stabilizer in the tank? Of course I could run in "hold" mode until the tank is empty, but that would screw up my lifetime MPG and I hate to do that, as silly as it sounds...
 

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I run almost exclusively in electric-only mode. The gas in my tank has been there for at least six months if not more. How long can I let it sit there before it "goes bad"? Should I put stabilizer in the tank? Of course I could run in "hold" mode until the tank is empty, but that would screw up my lifetime MPG and I hate to do that, as silly as it sounds...
The car will go into fuel maintenance mode when it senses it needs to. I think it needs well over a year. Another forum poster Ari C is legendary for driving all EV for over 20K miles. He did that by sitting parked burning all 9 gallons in an FMM session and modifying his system to avoid erdtt.

I'd say don't worry about it, don't mess with the system, let the car do what it must do when it wants to. But instead of filling the tank, just throw a gallon in there once in awhile.
 

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What LLninja said
 

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354 days of ownership and I entered fuel maintenance mode with ~0.4% fuel tank level left.
No issues with engine starting and I received a healthy 5.5L/100km on my last drive beforehand.

No issues with long storage in tank, provided you used high quality fuel to begin with. Can't speak for cheap no name stations or use of 87, though.
 

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I echo what the others have said and will add 2 thoughts:
- remember my first rule: "relax, enjoy your volt, the designers worried about all the details so that you don't have to"
- "Stale" is not principally a time based deterioration in gasoline, but rather mostly a combination of 3 effects:-1- evaporation of some of the more volatile components of the gasoline, 2- absorption of moisture and other airborne contaminants as air enters and leaves the tank due to normal daily temperature cycling and 3- oxidation or other reaction of some portions of the fuel. There are other lesser, slower issues also. The volts fuel tank is sealed and pressurized and this prevents or greatly slows all 3 principal issues. To complete the picture as others have noted, the car will run its engine periodically, typically every 6 weeks, if you don't and will consume the gas in the tank when its average age reaches some specific level. So if you don't ever use gasoline in your normal driving, eventually the volt will tell you that it is going to use some for you.
if you really want to avoid "screwing up" your lifetime mpg, then you can turn the car on in park and open the hood for 15 minutes every 5 weeks, which will run the engine without affecting the lifetime mpg calculation I think, but seems like a silly idea to me, to be reserved for only those honored few volt owners who have a quest to use no gasoline in their driving ever.... Just drive it and stop worrying....
 

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Engine Running Due To Temperature.

Starting in 2013 this setting is adjustable via the settings menu. Two adjustments cold and extreme cold. I. Forget what temps they are. I use to use extreme cold but last year I welcomed the lower setting. This allows the engine to come on to assist in cabin heating. This in turn will help your electric range by not eating up your battery with the electric heater
 

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As described in your Volt owner manual, Fuel Maintenance Mode tracks the AVERAGE age of the gas in your tank. When it reaches approximately one year, the FMM message appears, telling you to use it up or add more. You may postpone the process for one day, but once you start it, you will not be able to run on battery power until the gas in the tank no longer averages one year old.

Once you’ve started the FMM mode and the ICE is running, you can immediately end it, of course, by adding ANY amount of new gas. This drops the "average age" below one year, BUT the quantity you add matters a lot. Adding just a little new gas to a large amount of existing gas could mean that 1 month from now, the "old" gas is 13 months old, the small amount of new gas is 1 month old, and together the "average age" is 12 months, and the FMM shows up again. If you add enough gas to double the amount in your tank, the "average age" drops to six months, and your next FMM will occur in six months. If you drive until you run out of gas, the battery becomes available for use again, but the Volt goes into Reduced Propulsion Mode until you add gas. The advantage of ending the FMM by running out of gas is that you then know exactly how much gas is in your tank, the date it was put there, and that the next FMM won’t happen for one year no matter how much or little gas you just put in. (It also seems important to start the FMM so that you can end it; one recent report indicated the driver postponed the FMM, then added some gas, and the FMM message continued to appear when the car was restarted after refueling; don’t know if FMM actually kicked in the following day after the one-day postponement).

If you really don’t drive much using the ICE, why not just wait until the gas reaches the one year old average mark, and the FMM appears. Start the process and then drive using up the gas until it’s gone or nearly gone, and add the bare minimum that makes you comfortable. I myself drive 99% ev around home, but take one or two long drives each year. I try to time my last fill up of the trip to provide me with a comfortable enough amount of gas to get home, and still have enough to last until my next long drive, and if one year should pass before that happens, I don’t have much left to burn up to end the FMM.

The gas in your tank is sooner or later going to affect your statistics. The FMM, for example, is obligatory. You WILL use gas. You may be able to maintain an unbroken "ev miles driven between uses of gas" record by making sure your car is not moving when any gas is being used (e.g., running an EMM while the car is parked or leaving the hood up to run the ICE and use up old gas), but unless the computer splits the gas consumption data into "travel" and "non-travel" categories, every gallon of gas the car uses will be used to calculate both the MPG (total ev + total gas miles/ total gas consumed) and the MPGcs (total gas miles/ total gas consumed).
 

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If you are likely to be leaving fuel in your tank for a long time, the one recommendation I think useful to make is to use fuel with minimal oxygen content - ie avoid fuel with ethanol/methanol content if you can. This slows corrosion processes Paul mentions in post #5. The other two issues he mentions are dealt with by the design of the car - ie pressurised tank.

If you know you are going to do a long run ahead and you'll be draining the tank down, then fine to use any >91 octane.
 

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As long as your lifetime mileage figure is more important than the condition of your fuel system, go for it.
Modern gas formulations with ethanol do not store well. It is a well known problem. In my Volt I just run on the tank often enough to ensure it does nor become an issue. In my boats I add a product called Startron to the tank during long storage periods. I do not know if Startron is approved by GM for volts.
 

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Living out here in Seaside we have to drive well over 70 miles one way to go to any large city so we use gas on a regular basis. We still have over 157 mpg lifetime after nearly 24,000 miles on our 2014 Volt.
 
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