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Discussion Starter #1 (Edited)
After six months, I'm nearly at the end of my current tank of gas, and so I've taken an interest in what exactly happens if you DO run out of gas. So I'm going to document that here in this post / thread and will point to here from the FAQ.

In April 2011, Autoweek magazine did a test of the Chevy Volt which included running it until it was out of gas. They found that after running out of gas, the car continued on electric power for another 3-4 miles.

In Sept 2011, user bookdabook here posted his experiences ("Things I've Noticed #26"), and in item #2 there he described what happened when he ran dry. Click through for the full story, but in short A) after running out of gas the car continued on electric power at normal performance for about 2 miles, and B) just before it ran completely out of juice it went into "reduced propulsion mode" and then drove for another quarter mile or so. At that point it was really dead and he poured in the gallon gas he'd been carrying in the trunk during his test. :)

This week (below) a GM rep described the behavior like this: "You could have anywhere between 1 and 4 miles of range. ... As the Volt runs uses the remaining charge and heads toward the minimum allowed value, the available power from the pack is pinched toward the end to the point where no power is allowed for propulsion. The battery can handle this situation, but it is not recommended to do this on a regular basis."

I'm looking for reports from other Volt owners here on the performance of the car at that point, which I will call "limp mode". Does it still offer full performance? How fast can you go? How's the power (acceleration)?

Did you run your Volt out of gas? How'd it do?

UPDATE April 15th: in addition to the replies below, I did my own test as I finally used up all the gas in the tank, and reported on it here, comment 13 in this thread. Short version: enough power for highway driving for about 3.5 miles, then a rapidly depleting amount of power, enough to pull off the road and that's it.

For the record, here's a forum thread (and another) where we discuss running the car without gasoline, period. You can run the car's gas tank down to empty, and then charge it up (electrically), and it will drive just fine, although obviously without the comfort of knowing you have a gas backup when the battery runs out. Those two original thread posters had reasons for wanting to do this -- to defeat the gas engine coming on at temperatures below 25 deg F and thus eliminate the only gas usage they were seeing in their cold climate. When you first start the car, if the battery temperature is less than 25 deg F, then the gas engine comes on for a couple minutes to generate power to heat up the battery in a hurry. There's a lot italicized in the previous sentence, and every bit matters. By running on empty, you are defeating this function of the car that's there to protect the battery, so don't do that.
 

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Discussion Starter #3 (Edited)
Thanks Michael! I have reviewed that post and incorporated it into my post above. 2 miles full performance, then a quarter mile reduced power, then dead.

This is the only car that you can run out of gas on and still drive on to a gas station :)
(EDIT per below: OK, the only car you can drive at full performance after running out of gas!)

FYI, you can link directly to a particular post in the thread via the post number (e.g. #3 for this one) in the upper right corner.
 

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This is the only car that you can run out of gas on and still drive on to a gas station :)
I ran out of gas in a 2006 Ford Escape hybrid I had a few years back (TWICE) and it switched back to battery power allowed me to limp over to a gas station. The first time I drove about 2 miles at ever declining speeds from 50 down to 25. Not sure if that car had built in fail-safes to prevent complete discharge of the battery, however, or if I did any permanent damage. That car was almost as fun to drive as the Volt is now.
 

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When you first start the car, if the battery temperature is less than 25 deg F, then the gas engine comes on for a couple minutes to generate power to heat up the battery in a hurry. There's a lot italicized in the previous sentence, and every bit matters. By running on empty, you are defeating this function of the car that's there to protect the battery, so don't do that.
Despite the italics, I'm fairly certain this is not correct.

The engine turns on when the OUTSIDE AIR temperature is below 26F in order to heat up the engine coolant and provide HEAT FOR THE CABIN.

It also MAY put some electrical energy back into the battery pack if the power draw at that moment for driving the car and conditioning the cabin is less than the power being generated by the engine/generator, and some this electrical energy going to the battery MIGHT be used to help warm the battery pack, but this is not the reason for the engine turning on in the first place.
 

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Discussion Starter #7 (Edited)
I will happily correct the FAQ if wrong, but here is what I documented back in Dec 2010 when I was analyzing this.

From the FAQ entry on battery temperature management:

At low temps, the ICE may come on to generate power for the TMS to work faster, and to generate
power for the cabin heater, but only if the car is powered on (that is, the ICE won't start by itself; it will
only start once the car is powered on or it receives a remote-start command); the ICE will shut off once
it reaches 150 F. Note that the ICE coolant can not be used to directly heat the battery because the
battery coolant loop is separate.
There's a long article about the heating and cooling systems here, also from Dec 2010. I haven't reread it, but when I wrote the paragraph above it was based on several sources including that article. Certainly the temperature reading that drives the behavior is supposed to be from the battery pack itself, not ambient temp. Your battery pack may very well be at ambient if you've had it parked overnight!

Again I'll be happy to correct if pointed to high quality info that says otherwise. Anyway, it's a tangent. If anyone else has experience in running out of gas, let me know!
 

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This is the only car that you can run out of gas on and still drive on to a gas station :)
(EDIT per below: OK, the only car you can drive at full performance after running out of gas!)
Ha! My dad's 1959 Volkswagen beetle didn't have a fuel gauge. When you ran out of gas, while rolling along with the engine sputtering to silence, you reached under the dashboard, nearly to the floor, and flipped a valve that changed to a gas tank outlet at a lower level. So, you ran out of gas, but could then proceed at full performance (such as it was with about 32 HP) to the nearest gas station, fueled by the puddle at the bottom of the tank.
 

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That Fuel pickup was a popular mod to the VW's that had gauges later. It would give them a reserve, in case you did get too low. A VW with 32 hp wasn't too bad, of course it was missing a few safety features the Volt has.
 
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@ChrisC

When the Volt runs out of fuel, you will be informed with an "engine unavailable, add fuel" message in the driver's display. At this point, it all depends on the percentage of the state of charge remaining in the pack. You could have anywhere between 1 and 4 miles of range. If you were in Mountain Mode or Hold Mode, then you would have more range depending on how much charge is in the pack. As the Volt runs uses the remaining charge and heads toward the minimum allowed value, the available power from the pack is pinched toward the end to the point where no power is allowed for propulsion. The battery can handle this situation, but it is not recommended to do this on a regular basis. I hope this answers your question and saves you the trouble of experiencing "range anxiety" during your test.
 

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Discussion Starter #11 (Edited)
Growing up, my family had a VW Beetle as well, although it didn't have the "reserve tank" behavior your described. Just now I talked to my father and he confirmed that an earlier model Bug, from the 1950s, did have that. Brilliant! You just had to remember to flip it back to normal mode after filling up ...

Thanks Trevor for the info, I've incorporated it above. The "hold mode" you mention, that's for the Ampera, right?

"Range anxiety", very funny (tm). :)

I'll now head boldly towards an empty tank knowing I'll have at least a mile of range after I run dry!

Added to FAQ.
 
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@ ChrisC,

Yes, it is for the Ampera and export Volts.
 

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Discussion Starter #13
I ran my Volt dry today. It behaved pretty much as expected.

When the gas tank was completely empty, I got two warnings saying "propulsion reduced" and "add fuel". I then reset the trip odometer and continued to drive. Performance was slightly reduced; I normally drive in Sport mode and it definitely wasn't sporty anymore. But it drove just fine and I was able to accelerate enough and drive fast enough that I wasn't in the way of anyone or anything. I took it up to 55 MPH at one point (I was on a four lane road, not an interstate) and it did that no problem.

I drove it at moderate speeds, 25-45 MPH with lots of stops, for about 3.5 miles. At that point I was in a mall parking lot and expecting it to die soon. There was no further warning, but it then did suddenly get noticeably weaker and really was just limping. I also noticed that the air conditioning had shut itself off.

In total I got 3.7 miles out of it after the gas run out. It had enough performance to be on a highway for most of that, and at the very end it still had enough to be able to pull off safely if you were in traffic.

Great job GM!

By the way, I bought that tank of gas in August 2011 and drove 3400 miles on it! We haven't been on any roadtrips since last summer.
 

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Thanks Chris- this is great confirmation:)
 

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I did something similar last March when I drove to New York, I wanted to know how many miles you can go after the low fuel light comes on and you run completely out of gas. I ran the car in M/M so when the ICE quit after running out of fuel I still had 3 bars of electricity and was able to drive to a gas station.

Unfortunately I lost/misplaced the paper I wrote the miles to empty after low fuel warning, and I probably won't have the chance to do it again because I haven't used any petrol since March
 

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Discussion Starter #16
For me the low fuel warnings started at around 1.2 gallons, so around 40 miles of range.
 
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