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Discussion Starter #1 (Edited by Moderator)
I have enjoyed being a reader of this forum for several months now, and although not an active participant, it has provided me with ample information to help me become a new 2018 Volt owner this past weekend.

We were initially planning to order/lease a 2019 before the $7,500 tax credit expired.
However, two things happened that caused us to rethink that:

1) GM announced that the Volt was going away effective March 2019.
2) GM announced a 0% interest/72 month finance offer on 2018 Volts through 11/30/18.

Well, all of a sudden, we needed to change our plans. I got written email quotes from several Phoenix dealers (we live in NM with a very limited Volt selection), and we headed out the next morning. We were fortunate to find a suitable Volt at our first stop, and made the purchase by late evening. Not necessarily the color/options that we would have ordered, but hey, the final deal was just too good to pass up.

If you're still with me however, I do have a few questions:
the dealer recommended that we use only premium (91 octance) fuel to avoid fuel degradation because it sits unused in the tank potentially for (and hopefully) long periods of time.
and, to keep the tank topped off, due to the tank being pressurized.

From what I can determine, the manual only refers to using 87 octane. And most posts I have read here, would suggest keeping only a few gallons in the tank, and only filling it when taking extended trips.

I'd appreciate your comments.

2018 Volt LT (Silver Ice Metallic)
 

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Your dealer meant well but they are misinformed on both the octane required by your Volt, regardless of how often you use gas, and the desirability of keeping the fuel tank full.

The 2018 Volt is designed to run on 87 octane fuel. In some states clean air regulations allow 91 or 93 octane fuel to be sold that is ethanol free. In that case it might be worthwhile to use premium fuel in your Volt. If the premium fuel sold in your area contains ethanol then you might as well stick with regular 87 octane fuel. The Owner's Manual states you should always use Top Grade fuel, that means fuel from a major brand so you know the fuel contains all of the important automotive fuel detergent ingredients and other fuel additives.

Your Volt's fuel tank is sealed, pressurized except during refueling. The pressurized fuel tank satisfies a clean air requirement of all vehicles designated as partially zero emission vehicles (PZEV) by the California Clean Air Board (CARB). The pressurized system is designed to keep the fuel from evaporating into the atmosphere undetected. If your fuel system develops a leak, such as a loose or faulty fuel cap, the Volt pressurized fuel system will detect the loss of pressure and generate an error code. This system also keeps air and moisture from getting into the fuel tank but that is not its main purpose.

The Volt keeps track of the age of the fuel in the fuel tank through a software algorithm termed Fuel Management Mode (FMM.) After 365 days, if you have not used up the fuel the Volt's FMM will begin to automatically use up any remaining fuel in the fuel tank every time you drive the Volt. The only way to cancel FMM is to add a significant amount of fresh fuel to the fuel tank. So if you have 4 gallons of fuel that is approaching 1 year of age and you add 4 gallons of fresh fuel, the average age of the fuel in the tank will be 6 months and FMM will be suspended for an additonal 6 months. If you don't regularly use gas in your Volt the Owner's Manual recommends that you keep approx. 3 gallons (1/3rd tank) of fuel in the tank unless you are going on a trip. The Volt will start the gas engine for approximately 10 - 15 minutes every 6 weeks. This routine is controlled by engine management mode (EMM.) EMM will start the gas engine in your Volt to circulate the fluids and ensure that the internal engine components are properly lubricated. At the end of 12 months, if you never otherwise use gas the periodic running of the gas engine due to EMM will use approximately 2 gallons of fuel. Then it will be time to purchase 2 - 3 gallons of fresh fuel.
 

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jcanoe explained it pretty well. A few months ago I got a 2016 with under 20K miles. I too have read a lot on this forum about the car. Very useful.

I run the gas engine out of town some and mostly on the freeway at 69mph in a 65zone. When I head home I look at the range on electric that I have left and when I get within that range I switch off the gas. This uses some gas and eventually when I get to 2 bars I will put fresh gas in it. I limit my buying gas from just 3 stations in town that have proven to be trouble free gas for all my vehicles. Out of town, I use national brands.

I like the car and am still learning about how and what works best for me. I don't really care to squeeze every mile as EV but simply operate it in a way I don't have to think too much about it being special and just enjoy what it is.
 

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I didn't know about the sealed system required for zero emissions. Since the 70's North American systems were sealed (as opposed the Europe which where not). The gas cap sealed the tank. There was a fuel vapour separator cannister near the tank and a line went from it to the charcoal cannister(s) in the engine bay whereby the gas vapours were absorbed by the charcoal, any excess air pressure was vented into the atmosphere (I don't know how effective this was ie. if there was a small percentage of vapours getting through the charcoal). When the engine started up the intake manifold would draw some air in through the charcoal cannisters clearing them of vapours readying them for next time. I thought the gas tank pressurization was to prevent the lighter components in the gas (gasoline is made up of a number of chemicals, it is not a chemical unto itself) thereby delaying it going stale. I remember a segment of ICE Pilots NWT where they went to pick up a DC3 that had been siting for a year and it would not start. They drained some gas onto the snow and tried to ignite it and it wouldn't burn. They drained the tank and filled it with fresh gas, started right away and they took off into the wild blue yonder flying it back to Whitehorse. no one knows the actual age of the gas (at least a year) but it was a good example of why you don't want stale gas in your tank.
 

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Discussion Starter #5
Many thanks for the very thorough explanation. So glad to know that regular 87 octane is OK. Your suggestion re the ethanol contents is worth looking into.

My wife and I are both retired, and plan to enjoy using 100% battery power while in town, and gas up only when going out-of-town. So far we love this car, and for me personally (who suggested it), it's the best "basic" car that I've ever had.....basic meaning not a high-performance European import or similar.
 

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Discussion Starter #6
Thanks for the info. I see you are in Oroville, CA and so sad about your neighboring town of Paradise. I lived there in the 60's, and can't believe it's all gone. I loved that area, and used to bicycle ride up the Feather River canyon to near Susanville.
 

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I didn't know about the sealed system required for zero emissions. Since the 70's North American systems were sealed (as opposed the Europe which where not). The gas cap sealed the tank. There was a fuel vapour separator cannister near the tank and a line went from it to the charcoal cannister(s) in the engine bay whereby the gas vapours were absorbed by the charcoal, any excess air pressure was vented into the atmosphere (I don't know how effective this was ie. if there was a small percentage of vapours getting through the charcoal). When the engine started up the intake manifold would draw some air in through the charcoal cannisters clearing them of vapours readying them for next time. I thought the gas tank pressurization was to prevent the lighter components in the gas (gasoline is made up of a number of chemicals, it is not a chemical unto itself) thereby delaying it going stale. I remember a segment of ICE Pilots NWT where they went to pick up a DC3 that had been siting for a year and it would not start. They drained some gas onto the snow and tried to ignite it and it wouldn't burn. They drained the tank and filled it with fresh gas, started right away and they took off into the wild blue yonder flying it back to Whitehorse. no one knows the actual age of the gas (at least a year) but it was a good example of why you don't want stale gas in your tank.
The standard gas cap seal will still leak light hydrocarbons into the atmosphere. CARB's PZEV (Partial Zere Emissions Vehicle) and TZEV (Transitional Zero Emissions Vehicle) requirement is no leakage. In order to meet this requirement the fuel system needs to be pressurized in order to detect leaks. When you press the fuel release button the Volt releases the pressure from the system and unlocks the fuel door. Upon the next restart it pressurizes the system and locks the fuel door.

The Volt is a TZEV since it runs on electric most of the time.

As for that DC3, what happened was water collected in the fuel tank. Pressurizing the tank to prevent leaks works both ways. In addition, while you drive the gas is constantly being slowly mixed back together from the motion of the car. This is a passive mixing system. That DC3's gas hadn't been mixed so I'm sure stuff separated out.
 
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