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Discussion Starter · #1 ·
Today I ran a test (in the interests of science of course) and intentionally ran out of fuel. Added 1/2litre of regular87, ran out again, then filled with super. All the time running in "Hold" mode. Logging with a "Bluedriver" OBD2 sensor.
Results:
It ran for at least 50kms after the "low fuel" warning.
It ran for 11kms on the 1/2litre of regular fuel. Maximum ignition timing advance was 42deg, suggesting that there is no performance loss using regular. Sounded perfect, and I'm familiar with pinking noise.
After filling with Super, maximum ignition advance was again 42deg.

First conclusion: This thing rocks on fuel economy, even in Hold mode. I'm a life-long motorcyclist and I've only owned 1 bike that used less fuel than this 1800kg car. And running on electric is a total knock-out. My routine driving is about half-gas, half-electric.
Second conclusion: I can detect no difference using regular 87 compared to recommended super. I know this has been debated to death and I will always be using super in the future, but regular seems to work just fine, as long as you use the engine regularly. Just my opinion, please read and follow your manual.

Soooo, why oh why are there not more of these on the road!? Living in Nova Scotia I have very little electric vehicle support, and I took a chance buying this in Ohio and bringing it home, but so far I'm completely amazed at the car, and am in awe of Bob Lutz and his team.
 

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Soooo, why oh why are there not more of these on the road!? Living in Nova Scotia I have very little electric vehicle support, and I took a chance buying this in Ohio and bringing it home, but so far I'm completely amazed at the car, and am in awe of Bob Lutz and his team.
Very little to no advertising, so few people know about them.
Fear of the unknown.
Cheap gas prices.
And never having driven one.

I let a relative drive my Bolt EV yesterday. He was floored, very excited with the car. He thought it was a hoot to drive. I'm not sure what he imagined before the drive, but hands on the wheel driving the car makes a huge difference in people's reaction to the car.
 

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You'll need to do a few full tanks of each to see the timing adjust.
Even "dry" there is still some fuel in the tank - 1/2 litre mixed in probably didn't affect the mix much.

It's also the wrong time of year and location.
I suspect it doesn't matter for us, ever, north of the border. But in the hot desert of the south, likely does.

Thirdly, it's probably not something you'd ever see in normal operation. Only when the engine is pushed to max (which is rare for a volt). As it's a reactive process, it's not going to reduce the timings until a knock event occurs. It has no way of knowing the octane of the fuel you put in.

I don't really care though, because it's about $5/yr difference for me (or this year, a whopping $50 on my 11k road trip). I'll just use what the manual suggests. No need for science experiments :)
 

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The Premium fuel is suggested for longevity I believe. Idea being Fuel in the tank for a year or longer the top tier premium will have less degradation.
 

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Your sample in the test is too small an amount...unless you were to have set it up the way that The Mythbusters did by removing the old fuel tank from the equation when they were doing MPG tests
 

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The Premium fuel is suggested for longevity I believe. Idea being Fuel in the tank for a year or longer the top tier premium will have less degradation.
Yes, this is part of the reason for the recommendation.
 

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Contrary to popular belief, it is not for longevity that GM recommends 91 Octane for Gen 1 Volts. It's what the ICE in Gen 1 was designed for.

Does it work on 87 octane? Of course, it does. Does it work on extended drives? Of course, it does. Erick Belmer, the guy that drove his 2012 Volt over 400,000 miles, uses 87 Octane gas, and has nothing bad to show for it. Should you use 87 Octane Gas in your Gen 1 Volt? Its entirely up to you ... modern engines can easily adjust between 87 and 91 octane. And Gen 1 Volts ICE rarely gets taxed enough for 87 vs 91 to make a huge difference. GM engineers know the car the best, and they say you shouldn't be towing with the Volt (though many do), and they say you should not be using extension cords for the EVSE (though many do). They also recommend using 91 Octane (though many do not). So, if you use 87 Octane gas with your Volt, know that there are many others that do so, apparently without any adverse effects.

And longevity does not come with Octane rating. It comes with additives -- which are present both in 87 and 91 octane, if you get the gas from a Top Tier gas station. 87 Octane is recommended for Gen 2 Volts, but only from a Top Tier gas station. If you decide to put 87 Octane in your Gen 1 Volt, at least get it from a Top Tier gas station.
 

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Gasoline can lose some of it's octane in storage, and the Volt was designed to store gasoline in it's tank for up to a year, so it seems logical that Chevy would specify some "extra" octane to compensate for the loss. Some owners do not keep gas in their tanks nearly that long, so...
 

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Gasoline can lose some of it's octane in storage, and the Volt was designed to store gasoline in it's tank for up to a year, so it seems logical that Chevy would specify some "extra" octane to compensate for the loss. Some owners do not keep gas in their tanks nearly that long, so...
Almost all of the fuel in our 2013 is burned by Engine Maintenance and Fuel Maintenance cycles...can't remember when I actually was at the gas station to put fuel in our Volt...maybe 9 months ago??
 

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The Gen 1 engine requires premium for efficiency. They determined that the engine, when turned for premium, was more efficient. As stated you can run 87 octane, but what are you really saving? The Gen 1 was fully vetted to get the most out of a battery charge. Aero, tires, ICE etc. So, changing tires, removing the rubber spoiler, running 87 octane will affect the range of the battery.

The GEN 1 is probably the most over designed and pampered car in GM's existance. So, I'm sure you can do a lot of things that are not recommended without screwing up the car. Saving 20 cents on a fill up does not seem to be worth going against the factory recommendation.
 

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Discussion Starter · #13 ·
From ***-on-tour, below is the most convincing reply I have found, to this long-running repeated ad-nauseum question:

The timing tables (programmed into the calibration segments of the ECM memory) on the Volt LUU range extender includes specific levels of ignition timing advance specifically designed to take advantage of the higher octane for better combustion efficiency, reduced TWC loading, and maximize extended-range fuel consumption.

Any use of a lesser grade fuel will result in a significant amount of timing pull-back (aka knock retard) that will not only impact mpg but due to detect levels of pre-ignition detected by the knock sensors. However this process is not a memory mapped "learned" process, so this detection then roll back will get repeated each and every IGN cycle. Over time the repetitive detonation occurring will generate material damage within the combustion chamber and piston crown and could accumulate to failure levels through time, if regular octane fuel is used regularity.

Additionally GM testing has found premium fuel will degrade less through time in storage which in the Volt can be significant.
Hence the requirement for premium fuel.
It wasn't an error and it won't be changing anytime soon...

HTH
WopOnTour



Last edited by WopOnTour; 08-05-2014 at 06:40 PM.
 

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That is a worst case scenario, and one to be avoided, but at what ambient temperature, altitude, engine load and octane is that going to start happening? Some data has been gathered by owners during engine operation that suggests that it not happening all the time with regular gasoline. The safe bet is to use premium, of course.
 

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From ***-on-tour, below is the most convincing reply I have found, to this long-running repeated ad-nauseum question:

The timing tables (programmed into the calibration segments of the ECM memory) on the Volt LUU range extender includes specific levels of ignition timing advance specifically designed to take advantage of the higher octane for better combustion efficiency, reduced TWC loading, and maximize extended-range fuel consumption.

Any use of a lesser grade fuel will result in a significant amount of timing pull-back (aka knock retard) that will not only impact mpg but due to detect levels of pre-ignition detected by the knock sensors. However this process is not a memory mapped "learned" process, so this detection then roll back will get repeated each and every IGN cycle. Over time the repetitive detonation occurring will generate material damage within the combustion chamber and piston crown and could accumulate to failure levels through time, if regular octane fuel is used regularity.

Additionally GM testing has found premium fuel will degrade less through time in storage which in the Volt can be significant.
Hence the requirement for premium fuel.
It wasn't an error and it won't be changing anytime soon...

HTH
WopOnTour



Last edited by WopOnTour; 08-05-2014 at 06:40 PM.
That totally makes sense. However, I'm curious to know that does anyone who uses regular gas in a long-term fashion actually experience those symptoms?
 

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Would be 91 octane better for Gen 2 in long storage situation ?.
How long is the long term storage you are planning? In general it will not make any difference. The Volt's fuel tank is completely sealed so there is no way for moisture to enter the fuel tank. This prevents water from mixing with the 10% ethanol that is in most current gasoline sold for use in automobiles. In a few states Premium (high octane ) fuel is allowed to be sold that does not contain any ethanol. Also ethanol free unleaded gas (87 octane) is available in some areas. If you can find ethanol free fuel (est. $4 per gallon) it might be worth filling the Volt for long term storage.
 
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