• Nov 11, 2010
Hybrids like the Toyota Prius get excellent MPG, but, l... Hybrids like the Toyota Prius get excellent MPG, but, like all cars, they can run out of gas. What do you do if that happens? (Toyota)

Ask the mother of a teenage driver what piece of emergency equipment they want their kid to have with them in the car and mom will answer "cell phone." Indeed, the days of carrying tools, jumper cables, and a jerrycan of gas in the trunk are over – just call AAA.

But still, the question beckons: What happens if you're hypermiling in your Prius and you overestimate your skill? You can certainly run out of gas in a hybrid just as easily as you can in any car – and doing so is just as stupid. "But wait," you say. "There’s that big battery! Can’t it help me out?"

Well, that depends.

Dead In Their Tracks

Chevrolet's Tahoe and Silverado hybrids, for example, will not operate without gas in the tank. That’s right, they completely shut down if they run out of gas – no limping to a gas station on the battery, even if it’s fully charged. We know this because we tried it, thankfully when we were equipped with a three-gallon tank of spare fuel.

GM's official word is that driving these big hybrid trucks without gas leaves the large propulsion battery in vulnerable state, so rather than risk damage, the vehicles shut down. GM is not alone in this strategy, as Nissan's Altima Hybrid will also shut itself down the moment the gasoline engine runs out of fuel, lighting up a triangular warning lamp on the instrument panel.

Prius Survival Guide

Toyota's Prius, as well as the similar Lexus HS 250h sedan, will run on battery power even if it runs out of gas, but not for long. How far it can go is directly related to how much of a charge the battery has. With a strong charge prior to the gas tank hitting empty, some owners have reported being able to drive up to two miles without gasoline. When the battery becomes discharged enough that the gasoline engine would normally fire up, the Prius' speed will be limited to 18 mph, says Toyota. So on your limp to the gas station, you’ll be going pretty slowly.

By this point the voltage of the main battery, which can supply up to 650 volts to the drive motor when it is fully charged, has dropped so far that the drive motor is on the verge of drawing too much current. (Remember Ohm's law from high school physics?) When this eventually happens, the system shuts down the electric motor and the Prius stops where it is.

Since there is no conventional "neutral" in the transmission, pushing a dead Prius will be more difficult because the electric motor/generator system is also being turned. Which leads to a bit of a problem: If the car is flat-towed by a tow strap, it will be generating electricity and you risk overheating the motor. So, make sure your out-of-gas Prius only gets towed with the front wheels off the ground.

There's another problem to be dealt with when you run your Prius to a stop, and that’s getting it restarted again. When the main battery runs too low to spin up the gasoline engine, adding fuel isn't going to do any good. Charging the nickel-metal-hydride battery takes a special Frankenstein machine that exists only at Toyota dealers. Toyota, however, says that so far no dealers have reported ever needing to use the machine since the 2001 introduction of the car in the U.S. Still, you don't want to be the first.

Ford's Fusion Hybrid uses a similar strategy as the Toyota and Lexus systems, and will allow about a half-mile of driving on the propulsion battery after the Fusion runs out of fuel.

Stupid Journalist Tricks

We decided to experience what some daring Prius owners have reported, and drove a Lexus HS 250h hybrid, which has a similar driveline to the Prius, until it ran out of gas. We picked a non-highway loop with some mild hills and drove quickly enough that we were able to keep the main battery fully charged, but not too quick that we used battery power to augment acceleration.

When the trip computer alerted us that our distance until empty was zero miles, we kept driving. And driving. Two hours and about 55 miles later, the HS 250h finally ran out of fuel. At first it wasn't noticeable, except that the car was quieter. However, after only half a mile, the car became significantly slower, and wouldn't accelerate beyond 15 mph. We weren't yet in danger of killing the main battery, and so we added some gas and the car was back to normal.

How Low Can You Go?

Some owners of Prius' have reported that they can drive up to 100 miles after the low fuel light comes on. The big problem is that the remaining range is not always accurate. Trip computers that display cruising range cannot forecast the future, should driving conditions change.

You can figure, however, that with an 11.9-gallon fuel tank and a 50 mpg combined fuel economy rating, the range of the Prius is nearly 600 miles. Not only is this well beyond most vehicles on the road, but that's at least a good eight-plus hours in the saddle. There's really no excuse for not stopping for gas – or at least topping off the tank during a bathroom stop.

Editor’s Note:

Here's another warning: Don’t drive your Toyota hybrid for too long on empty, or you’ll eventually need to get towed to the dealer. Toyota gave us some more information about how its hybrids function once they’ve run out of gas after we’d published this story. It turns out we were lucky we didn't deplete the battery of our Lexus HS250h any more than we did when we drove it with an empty fuel tank. All Toyota and Lexus systems are programmed to attempt to start the gasoline engine when the battery reaches its “recharge threshold.” If the engine does not start after three attempts, the system shuts down and requires a technician to reset a fault code before the vehicle can get moving again, even if fuel is added to the empty tank. There is no way for a driver to know when the battery charge gets low enough that this automatic shut-down occurs, but it’s a necessary precaution to protect the battery pack from harm.

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    • 1 Second Ago
      • 7 Days Ago
      What happens when you run out of gas in a Honda Hybrid?
      • 7 Days Ago
      My 2003 Prius was recharged in by the dealer Syracuse ( spring 2010) by the last owner , just before I bought it. He had to wait about a week because " there are only 3 nationwide and they rotate to dealers as needed". The main battery ran down when the car sat in an auction yard for months. So that's at least 2 uses of Frankenstein....
      • 7 Days Ago
      AF4LG, 750volts isn't *********** more around 600 by usually multiple high voltage batteries. Typically these high voltage wires are colored orange to warn of the hazard. In addition to thse batteries is a small 12volt battery to start the engine, allowing it to still have a normal automotive electrical system for everything besides propulsion. These cars are an extreme hazard to firefighters when the vehicle has been involved in an accident, but at least the auto manufacturers made the wires easily distinguishable.
      • 7 Days Ago
      I will Stay old school, i love my ford crown victoria simple easy to maintain, a car that has not changed since 1992. why buy these hybrids you don't save any money in the long run,wait intill the battery dies for good you have to pay the dealer ship $5000or more for a battery for one those cars thats a lot of tanks of gas!
      • 7 Days Ago
      Ran out of gas in my 2009 Prius the first month I had it. The low fuel light came on and I went about 3 miles when the engine stopped. Radio and heater shut down automatically. I went 1 mile to gas station as I watched battery level decrease quickly, it was 5 degrees outside. Filled up tank and it took 8.6 gallons. Took it to dealer and asked what about the other 3 gallons of gas in the tank. They said they can try to recalibrate tank to gauge for about $600 - out of my pocket. If I fill up when gauge is on last square it never takes more than 6-7 gallons. Thanks Toyota for a car with a screwed up gas gauge.
      • 7 Days Ago
      I had an 07 Prius, put about 60,000 miles on it. I bought it when I had a 130 mile round-trip commute, I now have a different job close to home, so I sold it. I had two issues--I did run out of gas. I had tumor, was in really rough shape, and was headed to the specialist two days before surgery. I was really airheady. I jumped in the car and forgot it was really low on gas, I headed out of town, was between towns when I realized how low I was. I tried to make it to the next town. It ran out. I tried to run on just the battery, but that ran out about two miles from the next town. I hitched a ride to town,( I live in the Dakotas) and came back w/a gas can. It would not **************** had to be towed 45 miles to the dealership. THey didn't have to recharge the battery--but they did have to reset the codes. They couldnt do that over the phone, had to use a little box--it never even went inside--they did it in the lot and I drove off--they treated me like I was an idiot--I was really,really ill. (Am much better now)--second incident--we had back to back to back blizzards. It stayed parked in the garage for almost two weeks--we drove our pickup instead. The little battery died. The big batteries don't start the car, the little motorcycle battery in the back does that. It would not charge. We had to have it towed out of our garage to the dealership 60 miles away. They had to put boots under the tires to get it out of the garage--thank god the towing coverage on my insurance paid the bill. The dealership replaced the little battery,and reset the codes. They said we have to drive it every 7-10 days or that battery dies, which then causes the codes to be lost--there is so much electronic stuff on it and they drain that battery if it not recharged often enough. This second event happened 6 months after the first. We made sure to drive it, or at least start it, more often in the winter after this.
      • 7 Days Ago
      There will always be innovations to the Hybrid, things that you all probably have never even thought of are being done to make the Hybrid less energy consuming...you'll see hehehe, Just wait and see, you won't believe what Im thinking of ^.^It's already ebing experim
      • 7 Days Ago
      Last time I ran out of gas was in the late 50's when I was a teen. Never had that problem since. I own two hybrids....both owner manuals tell you NOT TO RUN OUT OF GAS. With the number of gas stations and opportunities to keep you car full of gas....you would have to be really stupid to put yourself in that situation. So what's the next experiment...see how far you can drive on flat tires????
      • 7 Days Ago
      Ugh, thanks for stereotyping all American drivers, especially us teens. AAA? Forget that, what are you driving that jumper cables, a tire iron, a tire pressure gauge and a good multi-tool can't be stashed somewhere? And as for a hybrid not being towable, this is nothing new. My Subaru can't be towed by anything other than a flatbed, even with a manual trans in neutral. And as for the difficulties of pushing it, how about this: Forget the heavy, in-efficient, eco nightmare battery packs, and build highly efficient cars the old fashioned way. Light weight, manual gearboxes, and either efficient turbo gas engines or clean diesels? Come on, I watched an episode of Top Gear where a European VW Lupo diesel got 75 mpg, while a Prius got less than 40. Speaks to the lightweight, manual, diesel format doesn't it?
      • 7 Days Ago
      Yea, great idea....but still not ripe. Nothing beats a V8 with a conventional gas tank and rear wheel drive. On the other hand you will find buyers for anything that is for sale.Sad but true "there is a sucker born everyday".
      • 7 Days Ago
      Well I do'nt know, but I drive an old fashion GAS engine car.... 15 years of driving I have never ran out of fuel.. Fill your tank up duh!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
      • 7 Days Ago
      If an Alternator, on a regular vehicle, can keep the Battery charged for several years, why can't an Alternator do the same thing for one of these peices of junk??? Surely one or two of these so called "experts" could find a way to add "pulleys and belts" in such a fashion to charge these batteries while driving. Of course, the reason they haven't already, could be so they can stick it to the customer for more dollars. Thank you for your time. TSgt., USAF Retired.
        • 7 Days Ago
        What turns the alternator, your moron? A running gasoline engine with GAS in it. No gas, no alternator charging a battery. A hybrid is no different and does charge its traction battery while driving. You must be a hater because I can't imagine anyone coming out of the USAF being that ignorant.
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