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2011 Chevrolet Volt's Extra 'Free' Electric Miles In Gas Mode


Once its initial battery charge is exhausted, the 2011 Chevy Volt seamlessly switches on its internal combustion engine to generate electricity.

But it turns out that the 2011 Volt can sometimes return to electric-drive mode even before it's plugged in, letting it deliver additional “clean miles." Here's how.

According to the very detailed range-traveled display on the center console, once the initial electric drive range is achieved, typically at 35 to 45 miles, the Volt is consistently driven by the gas engine until it is plugged in again.

The range-traveled display records the miles driven by battery, and then the miles added by the gas engine, and the EPA rates the gasoline-driven efficiency of the 2011 Volt at 37 miles per gallon.

2011 Chevrolet Volt drive test, March 2011

2011 Chevrolet Volt drive test, March 2011

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However, according to the Volt owner's forum, some drivers see mileage as high as 45 mpg while the gas engine is running.  On a recent trip, our 2011 Volt used only 2.78 gallons of fuel for 122.5 miles of displayed gas driven travel--which computes to just over 44 miles per gallon !

We have regularly seen lower gas mileage, closer to 39 or 40 mpg, on trips taken totally on flat terrain. This more recent 44+ mpg performance was achieved on rolling terrain, and a lucky observation yielded an insight as to how this better mileage is achieved.

The range-traveled display on the Volt separates battery miles driven from gas miles driven. Once the battery energy is exhausted, the gas-driven display is activated and records all additional miles until the car is plugged in again to recharge its large battery pack on grid power.

2011 Nissan Leaf and 2011 Chevy Volt, with charging station visible; photo by George Parrott

2011 Nissan Leaf and 2011 Chevy Volt, with charging station visible; photo by George Parrott

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However, in the recent rolling terrain drive, I had switched the central console display to "power flow" mode which reports in animated presentation exactly where power is going and coming from on a moment by moment basis.  

Not too surprisingly, I saw regeneration braking send power to the battery during any downhill, even while the cruise control kept the car at 63 miles per hour I had set. I was adding battery charge via the coasting and braking process, just as even a standard Prius hybrid does.

However, what surprised me--and it has also now been reported by others on the Volt forum--is that the Chevy Volt, once it has recharged the battery via regenerative braking, will then switch back to electric-drive mode for as much as 2 or 3 miles. BUT, this range is recorded under the gas-driven mileage!

2011 Chevrolet Volt drive test, March 2011

2011 Chevrolet Volt drive test, March 2011

Enlarge Photo
As JeremyK on the Volt forum points out, the extra range comes from recapturing energy first provided by the gas engine in going up those hills. So it's only reasonable that any supplementary electric drive miles be included as fuel-driven, and not from the power provided by plugging in the car.

So, the powerful regeneration in the 2011 Chevrolet Volt adds hidden fuel-free miles to the Volt's total range, which actually increases real-world gas mileage.

The EPA mileage tests do not incorporate this kind of regenerative energy recapture in their standard test cycles, which explains why most new Volt drivers are actually getting better than EPA ratings for their real-world gas mileage.

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Comments (6)
  1. Just exactly how is it possible for the EPA tests to "avoid" the recapture capability? They are driving
    the car and measuring the gasoline consumed, thus should certainly be including any regen benefits. They do so in their city mode, obviously, otherwise their mileage would be far less. If, in fact, they are somehow not taking regen benefits into account, that mean their tests are invalid. Give them a call, see what the morons say. It only took them 2 years to
    figure out that MPG doesn't apply to EVs.
     
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  2. @Ramon,
    The EPA cycle does not include anything like significant hills, so there is little downhill to strongly recapture battery power. There are a number of stops, but that will produce relatively little in terms of strong regen compared to a mile or more long downhill.

    Felix Kramer commutes from SF to Lake Tahoe (6000') at least once a month; he has reported to me getting 50+ mpg for his ICE segment of that trip DOWN from Lake Tahoe since so much regen occurs and adds "free" battery miles that are recorded on the Volt display still as ICE miles.
     
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  3. Ramon, turns out, the EPA does not drive the cars. It is ALL done through a computer simulation. That is why it misses the regen miles after gas engine cuts on.
     
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  4. @JP: Not quite. Manufacturers submit their fuel-efficiency data based on emissions calculations. The EPA reserves the right to test any vehicle at any time, but in practice it tests only 10 to 15 percent of the vehicles on sale in any given year. FYI.
     
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  5. It's not "free" miles. Regen occurs due to two situations - (1) deceleration after a previous acceleration or (2) a downhill run after an uphill climb. due to system efficiencies, you get back some of the energy you expended. It's the normal result of good hybrid operation.
    Now in the Volt case, If you spent your electric battery climbing the hill and then it kicks into gas mode on the downhill, then your ICE MPG will look great, but, you still paid for it with your electric charge. Do your own system analysis on other possibilities, and you can get a wide variation in result for either the electric or gas portions of your Volt trip if it envolves both modes in unequal terrain conditions.
     
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  6. Ok, a better article might be to do a test to determine 'normal' mileage if you use the Mountain Mode recharge process to capture these 'free miles'. Based upon previous other postings, the Volt can get into the mid-40s MPG on the ICE in Extended Range by actively using mountain mode. I stared doing so on my 164 mile commute (going to normal mode when driving under 55 MPG and mountain mode above such as much as possible). Doing so, my total gas consumption dropped from a high of just over 4 gallons to a low of exactly 3 gallons (same 164 mile one way trip starting will full battery obviously). By the way, there is significant incline/decline during such which adds about 3 miles of range on the backside.
     
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