Chevy Volt: Why's The Engine Running?

One of the main reasons why bought a Chevrolet Volt was to be among the first to experience and report on its performance in harsh winter conditions. It didn't take long. Our first charge in the Midwest and the 24 hours that followed were enlightening, especially because of unexpected gas-engine activity.

We charged the car at 240 volts at the InterPark parking structure across from our headquarters. As the car's display had predicted, the Volt was fully charged in about four hours, maybe a little longer. Cold temperatures can slow the charging, and it definitely affects the range. It was 20 degrees outside. Even when topped off, the Volt's estimated electric range was 35 miles rather than the 40 miles I witnessed in my initial test this past fall.

When I arrived home 17 miles later, only 10 miles of electric range were left. Why wasn't it 18 (35 minus 17)? Mainly because traffic was crawling, it took more than twice the normal time to get home, and I set the heat at 68 degrees in Comfort mode, the one that prioritizes comfort over efficiency. My seat was on auto-heat, too.

On a separate trip, I witnessed the opposite.

I left home with 15 miles of range, met little traffic and arrived 17 miles later with 5 miles of electric range to spare. I think this has more to do with time than miles. More time equals more electricity used to keep myself warm. The distance was the same, and experience suggests the Volt is roughly as efficient at low speeds as it is at high.

During that first journey, I was on the road for only a couple of blocks when I was surprised by the gas engine turning on, accompanied by a notice on the instrument panel that read, "Engine running due to temperature." This happens strictly to provide cabin heat, according to Chevrolet. The electric heater isn't always powerful enough to warm the cabin by itself in subfreezing temperatures, and if it were, it would drain too much battery power. The design is a delicate balance that attempts to be efficient in the long run.

Internal combustion engines are only about 20%efficient, so one could argue they're actually better at producing heat than anything else. It's not just wasted idling, though: The engine drives the generator and stores some electricity in the battery pack. The engine was on for only a minute, maybe two, at the beginning of that journey of over an hour, and apparently that was enough for my circumstance. Outside temperature, speed, wind and sunlight affect interior heat.

I could reconcile this behavior because I recognize the goal is long-range efficiency and because a negligible amount of gasoline was used. But I know people tend to fixate on electric-only operation — in this and in conventional hybrids — regardless of the bottom line. There will definitely be objections.

Although I understand the principle, I didn't expect it to happen when the car had been plugged in, which allows the Volt to keep its battery in a target temperature range, and I definitely didn't expect it when the car still is plugged in.

One of the car's attractions to me was its ability to pre-condition (heat or cool) the cabin via remote start, using the key fob or through OnStar using or an iPhone app. I had assumed this would be 100 percent electrical, but at least once when I tried it, the engine started. I have an unheated attached garage, and I thought the Volt would be my chance to use remote start without leaving the car out in the snow, but apparently it's not meant to be.

Senior editor David Thomas attempted the same type of remote start on a 20 degree morning and the engine did not kick on. When he got in the car 10 minutes later it was warm in the cabin and the motor was the lone powerplant until he had driven about a mile in the frigid temps. He also has a detached garage and had the door open during the warm-up.

Perhaps Chevy can program the car not to start the engine in situations like this at all times. Given enough time in a wind-free garage, the onboard electric heater would raise the temperature substantially, even if it didn't hit a target temperature.  Without a provision like this, it's not worth the risk of firing up the gas engine in my attached garage.



It's nice to see how it functions in the real world.

Amuro Ray

My take on this is how it has invalidated many Volt's support belief that Volt will run on pure electricity without ANY gas being used.

I blame it on the utter failure of GM's marketing to disclose such info! It's not even readily available in its webpage.

Amuro Ray

"invalidated many Volt supporter's belief that Volt will run on pure electricity without ANY gas being used even for commute purpose (enough charge in battery)."


Kind of impressed with this, actually. Shows a tremendous amount of thinking and planning on GM's part that we haven't seen in the past when designing vehicles.

Perhaps the company has finally learned its lesson?


In a close garage, When pluged in and engine ruining, the toxic air will for sure at least create serious health problem. Unthinkable.

many people park their remote start vehicles in their garages. It's pretty common sense to open the garage door before starting any of those vehicles. However, it may need clarification for Volt owners on this. For the record, I have a detached garage and opened the door to see the car's lights go on when I hit the remote start, and for me the engine did not kick on until I drove off.


One solution would be to have the car look at the front and rear collision avoidance sensors. If both the front and rear are blocked, assume the car is in a garage and don't start the engine.

EV-hater right here


@ D.T.

J.W. said when Volt is still pluged in, the engine kicks on. If the car starts automatically for maintaining the target temperature , it very likely happens in the middle of night in very low temperatrue areas. If the car is in a attached, close garage, the fume will create serious health problem, or kill people inside the house, when temperture is very low,or simply malfunctioning .

Hope J.W can helps clarify the situation a little bit clear whether the car simply starts itself automatically for maintaining the target temperature.


So if I'm understanding this correctly, the engine fired up with J.W. when it was parked and plugged in for pre-heating. However, with D.T., it did not, when basically doing the same thing. Was there an extreme temperature differential?

It seems like this is something GM could easily address in the car's programming. I can understand the motor kicking on for extra heat once the car is underway. Surely they can program the car to NOT start the engine if it's currently plugged in - maybe they just didn't think to do that yet?


Here in SoCal where the lion's share of the Volts will be purchased, we hardly ever use the heat in the car, so that is not such a big deal. However we do use the AC quite a bit. I used the AC in my Honda this morning Jan 24th, so I can assume that I would be using the AC in my future Volt quite a bit. I have always assumed that AC, heated seats, the stereo, GPS Nav, cell phone chargers, head lights, etc, etc, will always impact the electrical charge on the vehicle. I have been told that most cars are more fuel efficent running the AC than with the windows rolled down as that increases drag. I'd like to hear from more SoCal drivers how their Volt is performing.



Guess the temperature should be maintained at above certain degree when charging, so that the battery can be charged fully. If Volt is parked outside and stays uncharged like D.T. case, there is no need to start the engine to warm up the battery


The Volt can't start the gasoline engine when it is unattended, plugged in and charging. The preheating function operates off the charging current, not the gasoline engine.

The engine can turn on when it's plugged in ONLY if you use the remote-start feature -- not otherwise. I saw it do this only once in my brief time with the car, but when I asked the Volt's chief engineer, he confirmed it can happen, depending on temperature. If the car's parked out in the cold, NOT plugged in, remote-start works almost like it does for a conventional gas car with remote start: The engine is practically guaranteed to start unless the temperature in the cabin is already where you'd want it.

If you DON'T use remote start:

The car doesn't start the engine when charging or when it's still plugged in after the battery is full. An electric heater (powered by the grid) maintains the battery temperature. From what I can tell, the current draw has been less than 0.3 kW once the batt is full. (It's over 3 kW when charging.) Because the battery is relatively warm when you go to drive the Volt, its capacity is higher, thus so is the range. Chevrolet also says keeping the car plugged in when the temps are below freezing is critical to maximize the battery's lifespan. From the owner's manual:

"Do not allow the vehicle to remain in temperature extremes for long periods without being driven or plugged in. It is recommended that the vehicle be plugged in when temperatures are below 0°C (32°F) and above 32°C (90°F) to maximize high voltage battery life."


Amuro Ray

I wonder if this will subject the Volt to the 1st recall - something on the owner's manual or a caution warning sticker. It is, after all, a situation that can lead to fatality with proper usage but without you knowing it.


What about the engine block heater?



Did you actually read what jw wrote? The engine will not start uunless you activate the remote start function in extreme cold. The fact that the volt needs to use the engine to generate sufficient heat in cold weather should tell you something about what it must be like to drive a Leaf when its below freezing outside. My guess is a pure electric car won't get comfortably warm on a very cold day.


Joe W,
Thanks for the very clear explanation of those functions of the Volt.


Now you know why GM is encouraging folks to Lease rather than Buy. With leasing the potential of lawsuits is substantially less. I would much rather have a Fiesta or Prius than this $40,000 experiment. NOT on my dime Chevy!

The engine drives the generator and stores some electricity in the battery pack. The engine was on for only a minute, maybe two, at the beginning of that journey of over an hour, and apparently that was enough for my circumstance

What if the little ones touch the remote start without the parents knowledge? Can it be running in the cold garage without anyone being aware?


Could you try this experiment?
Put a small 120V electric space heater inside the car.
500W for a few hours will be plenty.
See if the engine runs.

Even if the engine kicks in, you will still save on energy from the battery pack.

Body Shop owner

bro if the little ones touch the remote on any normal car it'll start not just volt.

bob gaito

im not sure what year volts you're refering to but my 2013 has a feature in settings and preferences...i think under climate control...where the engine will not start when the charge cord is plugged in...i checked the box and problem solved!

Kevin Eldridge

Thanks Bob Gaito for pointing out the settings and preferences. While I wasn't able to turn off "engine assisted heating" for my short commute, I was able to change the setting to only use "engine assisted heating in very cold weather" as opposed to "cold weather". I'm hoping this will use less engine. Our electricity in Woodstock, IL is quite inexpensive, and I have a short commute to work (3 miles). I hate to use gas for that.


fior the 2013 volt if you go to the config and settings menu and under that the climate control settings, there is a checkbox for "plugged in engine assisted heating"

I believe the default is for the box to be checked. Uncheck the box and it won't happen. If you are outside you may want this engine assisted heating to happen. It seems to me the factory defaults should be not to have this checked for safety reasons.

Personally I would test this while standing next to the car in cold weather.

You can choose when you want the engine assisted heating to kick on... you check cold weather (35 F) or very cold weather (15 F). I believe the factory default is 35 F). I believe they should allow you to check never use is you want, but what do I know?


the last paragraph above was meant to address the engine assisted heating when you are driving and you don't want the engine kicking on when it is below 35F.

Not sure how/if these vehicle settings effect the remote start.


When the volt is plugged in the engine will never start when heating the cabin. If the car is not plugged in to grid power, and remote start is selected, the engine may start if the temperature is below -4C, but if plugged in, it should never start regardless of the outside temperature. If yours is, then that is a malfunction.


Does the grid not only charge but also heat the battery in cold weather? If the battery is toasty due to this (putative) heating process, why doesn't it charge to the normal cruising distance? Does it know the state of its wheel bearing grease and the like as it charges, and subtract miles due to increased resistance? That seems a bit much.

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