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Discussion Starter · #1 ·
I have been in Fuel Maintenance Mode for a week. I have driven about 50 miles. I started the week with a full charge, giving me an EV Range of 66 miles. Now the car is showing a EV Range of 43 miles. Why is the car losing EV Range while it is in Fuel Maintenance Mode?
 

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Have you been using your air conditioner? I believe the Volt will use the main battery for this even in FMM.
 

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Have you been driving more aggressively in FMM? The projections of both EV and Gas miles are affected by your driving style. ie Drive it like you stole it in Gas mode will have an impact on projected EV miles and vise versa.

VIN # B0985
 

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Discussion Starter · #4 ·
Yes, I have been using my air conditioner, sometimes. I will turn it off and see if the EV Range stabilizes. No, I have not been driving more aggressively. Hard to do in the stop and go traffic I face commuting every day.
 

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Options:

  • Start the car while parked and burn off all the fuel (Ari_C does this to maintain his 20k+ mile all EV miles status)
  • Add a gallon of fresh fuel to kick the can down the road
  • Road trip!!! How about Disney?
  • Switch the center console to anything else but the energy screen and don't worry about it
 

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Why is the car losing EV Range while it is in Fuel Maintenance Mode?
During the week you have been running the FMM, you admit to using the a/c while driving. It is likely then that your Volt may have also been carrying out battery maintenance procedures during times when the car was parked and/or overnight. This consumes battery power. If you have not plugged into the grid since the FMM started, this use of power would contribute to any changes in estimated ev range (are all 10 power bars still green?). Even if you have plugged in each night, this battery activity itself could contribute to a recalculation of anticipated range.
 

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Put it in hold and run her out.
 

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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
 

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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
What did you do when you drove an ICEr? You had no choice but to park a warm car in the garage. I wouldn't worry about it and just let FMM happens when it does. If you want to postpone it, add a gallon of fuel. On the other hand. Not ever hitting the dino juice means you're not going out much, head to Seattle or some national park or something.
 

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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
At this point, I'd just start using the Volt for longer trips. A couple of 200 and 300 mile trips and the gas will be gone before you know it.
 

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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 Volt will run Engine Maintenance Mode (EMM), starting and running the gas engine for approx. 10 - 15 minutes, once every 6 weeks if you don't otherwise use any gas. The Volt will enter Fuel Maintenance Mode (FMM) every 12 months, FMM will start to use all of the fuel in the tank. If you add fresh fuel to the existing fuel in the tank the Volt will compute the average age of the combined old and new fuel that is in the tank. Adding 1 gallon of fresh fuel to 8 gallons of old fuel will not delay FMM for very long. If you add 4 gallons of fresh fuel to 4 gallons of old fuel the average age of the fuel will be reduced by half, delaying FMM from running for up to 6 months.

If you don't regularly use your Volt's gas engine the Owner's Manual recommends keeping the fuel tank 1/3rd full (approx. 3 gallons of fuel.) Over a 12 month period EMM would run 8 to 9 times and use approx. 2 gallons of gas. Once FMM starts the gas engine would start and begin using up the remaining gas in the tank (approx. 1 gallon.) Then it would be time to add 2 - 3 gallons of fresh fuel to your Volt's fuel tank.
 

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Discussion Starter · #12 ·
I indicated that I would see what happened when I drove without the air conditioner, while in fuel maintenance mode. A 5.5 mile trip still reduced by EV range by 2 miles. (This trip is mostly uphill and would usually reduce my EV range by about 10 miles.) I then turned on the air conditioner for a shorter trip and it reduced by EV range by much more. So it seems that even in fuel maintenance mode, the Volt will not necessarily work the engine hard enough to maintain EV range. My understanding is that fuel maintenance mode is like hold mode. So that raises the question of what the Volt does when it the EV range is zero. Perhaps the engine works harder when EV range is 0 than it works in hold mode/fuel maintenance mode when there is EV power available?
 

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Put it in hold and run her out.
During a Fuel Maintenance Mode operation, Hold Mode is superfluous. Once the computer determines the "average age" of the gas in the tank is ~12 months old and you say Yes to the FMM request, the ICE starts up and you can’t run on battery power again until something is done to reduce the "average age" of the gas in the tank.

I’ve experienced 2 FMMs, but I drive a 2012 Volt, so I don’t know if one can actually switch into Hold mode while running an FMM. I also don’t know if you could switch into Mountain Mode and use a little of that "old" gas to recharge the battery up to the MM-maintained level if the FMM message happened to appear when your battery was depleted or if you postponed the FMM for a day in order to deplete your battery before starting the FMM just to use some gas for this purpose (although Gen 1 MM-recharging uses only ~0.36 gallons of gas, so you can’t really use up a lot of "old" gas by doing this).
 

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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...
 

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I indicated that I would see what happened when I drove without the air conditioner, while in fuel maintenance mode. A 5.5 mile trip still reduced by EV range by 2 miles. (This trip is mostly uphill and would usually reduce my EV range by about 10 miles.) I then turned on the air conditioner for a shorter trip and it reduced by EV range by much more. So it seems that even in fuel maintenance mode, the Volt will not necessarily work the engine hard enough to maintain EV range. My understanding is that fuel maintenance mode is like hold mode. So that raises the question of what the Volt does when it the EV range is zero. Perhaps the engine works harder when EV range is 0 than it works in hold mode/fuel maintenance mode when there is EV power available?
You don’t know if your car is losing ev range or merely experiencing fluctuations in ev range estimate calculations since you can’t run the Volt on battery power until the FMM in completed. I’m not sure if the variations you see in the estimated ev range are significant (i.e., something is actually consuming net battery power as you drive), or merely changes in the on-the-fly range calculations (do you equally wonder about the changes in gas range estimates when running in Electric Mode?).

Again, the question is, are you seeing any reduction in the number of green bars of available power as you drive (if not on the driver’s display, then on the center screen power flow display)? Does turning on the air conditioning eventually decrease the number of green bars, or does it just affect the ev range estimate? If the car were actually pulling power from the battery as you drove and not replacing it, seems to me that would show up in the display by reducing the number of green battery bars. If the car was pulling power from the battery while you’re not driving (for battery maintenance, etc.), that, too, should show up in a reduced number of green bars. A 5.5 mile drive uphill would be expected to reduce estimated ev range after recalculating for uphill mileage vs flat terrain mileage (because you aren’t actually using power to drive uphill, the reduction in range is less than it would be when you also consume power as you drive uphill). Are you plugging in overnight? If so, do any of the OnStar data supplied sites (Voltstats, MyVolt, MyChevrolet) indicate that significant power is being used to recharge overnight?
 

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The 2016 Volt is more fuel efficient on regular gas than nearly, if not all, the econo box cars out there. I say, don't be afraid to use it once in a while. Even though we use the gas engine quite often after 21,000 miles we still have a 148 mpg lifetime average...
 

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With all these people talking about the intricacies of FMM (and EMM) I've never seen either. My 50 miles per day commute means I hit dino juice daily unless I hypermile like a crazy man or happen to get the one free charging station near work. With my youngest heading to boarding school, I am no longer constrained by her schedule, so I could leave for work much earlier and get that spot almost daily. Then I might be able to experience this FMM - but I doubt it. With boarding school will be some long trips to pickup and drop off on weekends, so dead dinosaurs will be burned...
 

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With all these people talking about the intricacies of FMM (and EMM) I've never seen either. My 50 miles per day commute means I hit dinomjuice daily unless I hypermile like a crazy man or happen to get the one free charging station near work. .
Are you fifty miles one way? Mine is fifty four round trip, my return leg is longer than going in because traffic changes enough to warrant it. On my Gen2 I am averaging 66/67 on the guess o meter. Now except for brief portions of my trip, figure eight to ten miles max, which are at 55/65 speeds most of my trip is on 35/45 country roads.
 

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Are you fifty miles one way? Mine is fifty four round trip, my return leg is longer than going in because traffic changes enough to warrant it. On my Gen2 I am averaging 66/67 on the guess o meter. Now except for brief portions of my trip, figure eight to ten miles max, which are at 55/65 speeds most of my trip is on 35/45 country roads.
I have 50 miles round trip, but am driving a G1, rated for 38 miles of range, and I think the best I've ever done was 52, but that was driving like a grandpa. I now slapped on 18" wheels and drive like Jeff Gordon, so the trip is a who lot more fun, but I will never achieve 50 miles of EV range without a charge in between.
 

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Discussion Starter · #20 ·
I will respond to wordptom by putting in quotes one of his comments and then providing my answer. "You don’t know if your car is losing ev range or merely experiencing fluctuations in ev range estimate calculations since you can’t run the Volt on battery power until the FMM in completed." This does not seem consistent with what I am seeing. At the beginning of the FMM week, I had 66 miles of EV range, with the battery fully charged. I consistently lost EV range after each drive. At the end of the week, I had 35 miles of range. While I did not regularly charge the Volt--I did not see the point--I did charge it a little when I made two shopping trips because the charging was free. In both cases, I gained EV range, which seems to indicate that I was depleting the power in the battery while driving in FMM. Further, the myChevrolet app, indicated after these short charging efforts while shopping, my battery was charged at about 65%, down from 100% at the beginning of the week. I think we can reject the hypothesis that driving on FMM was not depleting the battery.
 
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