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May 10, 2007
What happens when a Prius runs out of gas?
Good question. And I’ll tell you the answer since I know from first-hand experience.
As you may know, a Prius is a hybrid car. This means that instead of one big engine, it has two small engines—one gas, one electric—that are connected to the drive train by a fancy computer-controlled clutchy thing. (Very technical, I know.) When you are scooting around town in mall parking lots, you mainly use the electric motor, and when you need more umph to get on the freeway, the gas motor kicks in and helps. And when you stop, both motors turn off. There’s even a little display that shows you what’s going on under the hood. The battery stays charged through a combination of coasting/braking and the gas motor, so there is no plugging in. Neat, huh?
I’ve often wondered what would happen if it ran out of gas, and I found out yesterday. I was cruising down 210 in the carpool lane with the wife and kid on our way back from Glendale. I had noticed we were low on gas when we set off toward Glendale, but the Prius is deceptively fuel-efficient and the blinking “add fuel” light tends to cause little alarm. I was blissfully ignorant.
So here’s what happened. Suddenly, the car made a loud beep, and no less than 4 red lights came on. None, of these lights, btw, indicate you are out of fuel. It just looks as if something has gone horribly wrong with the engine. At this same time it felt as though the car had lost all power, but I was still coasting along pretty good. I quickly made my way over to the right lane, but there was a fairly steep grade looming before the exit ramp. I was afraid I would soon be pushing this car. So I hit the button on the steering wheel that shows the fancy motor display, and just as you might expect hope, the electric motor was still operating and I made it off the freeway and to a gas station with very little trouble at all. In fact coasting/braking was still charging the battery.
After I had some fuel in the car, I powered it up. The red lights went away, and it was brand new again. Man, what an awesome little car! I admit, I had my doubts when we bought it, but every time I drive it, I love it a bit more.
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May 17th, 2007 at 12:25 pm
Hi Mike,
The very same thing happened to me last night, with my 2007 Prius… Which is about 2 1/2 weeks old. I was driving back from Santa Barbara, on my way to Rancho Palos Verdes. I took PCH to avoid the wretchedness that is the 101/405 at rush hour. At about 420 miles, my car beeped to tell me it was time to refuel. I of course ignored it, partly because I new there was still more gas in the tank, and partly because I’m still in the testing phase of ownership. (I’m still learning all the tricks it can do.)
In my head, I was thinking, “Hey, my last tank was 506 miles. I should be fine… but why did it beep so early? Oh, must be all that air conditioning I used today, and the equipment I’m hauling right now. Well, there should be about 3 more gallons left. I figure, even if it doesn’t get the average 45 per gallon, I can estimate about 30 per, right? Hmmm, I’ve got about 40 miles ‘til I get where I need to be… I should be fine. Beside, I’m already running late…!”
So, I continued the race. As I headed into Rancho PV, I began eyeing that blinking square more often. I started to get a bit nervous, as I checked the time and started thinking about that steep hill I was about to climb. “It’s only 2 miles up the hill, I should be fine,” I kept telling myself.
The light turned green, and I started up the hill. Almost immediately, I felt the power start to go. “More gas, more gas!” Nope, didn’t do anything. I checked the consumption screen and watched wide-eyed as the battery indicator turned from blue to purple and the bars disappeared like that [snap!]. “I think I can, I think I can!” No, really you can’t. Barely a quarter of the way up, the car slowed to nothing, and I had to pull over. Oh crap. Time to call AAA. “Help, I did a stupid thing, and I need gas!”
So, the guy came to put 2 gallons in, but the engine still wouldn’t start. It kept saying “Add fuel.” (I won’t go into the details of how he thought I didn’t know how to start my car and had to try himself.) The light was red on the power button, the panel didn’t say “READY,” and when I would try to put the car in drive, it would stay at neutral. Hmmm, must be the incline preventing the sensor from sensing the fuel. Sorry, honey, gonna have to tow you to the nearest gas station.
We headed to the station so I could gas up. I took me a couple “restarts” for the car to sense the full tank and start up. WHEW! Lesson learned…
July 22nd, 2007 at 3:08 am
I just treat each square as one gallon. If its blinking I stop at the next gas station regardless of price or grade of gas (three gallons of premium [you get the worst mileage on premium] is better than being stuck on the side of the road).
I say three gallons because about that amount it what it takes to trigger the fuel gauge to recalculate.
July 15th, 2008 at 5:35 pm
I was on a long trip with friends when the same thing happened. Darby was driving from the u.p., and ran out of gas. He said there were three bars, then two, then one…just like that! I didn’t drive this rental car so I don’t know if the bars are just the battery (if it is, the need a better battery monitor system). We were on a VERY minor upgraded hill. A Lansing firefighter stopped with a few gallons of gas. That didn’t start it. I tried finding in the book how to start it after running out, or how to force it to start the gas engine, but to no avail could I find it in the book. We had to push it uphill to a gas station with an MSP officer behind us as an escort. Once at the station, he put more fuel in it, and it started. LOL, the MI State Police officer waited around while we were huffing from pushing to be sure we were okay, and weren’t going to have a heart attack.
September 11th, 2008 at 6:33 am
In my experience, the Prius runs out of gas completely with at least one full gallon still in the tank. It’s as if the capacity is 10.9 instead of 11.9 gallons. (Using the average mpg and distance traveled you can figure how many gallons you’ve used more precisely than the gauge bars indicate.)
Once that beep and all the warning lights happen, DO NOT COME TO A FULL STOP. I found that you cannot accelerate again, so your slowest speed will remain your maximum speed. And if you stop the motor/transmission will go into full shut off protection mode. Then you will need quite a few (maybe three?) gallons in order for the car to realize that more gas is in the tank. I am not sure whether it will come out of its protective mode by itself, or whether it has to be reset by a technician. (I ultimately had to have mine towed to a dealer.)
March 11th, 2009 at 6:57 pm
This happened to us, too. The first time, we were really freaked. First, I was kicked out of cruise control. Then, the beeps and lights started. (No kidding – they really should have a warning that comes on saying the engine can’t work because you are out of gas, not all those exclamation marks and caution signs, which don’t tell you anything.) The idea that we were out of gas didn’t occur to us, as we thought we had the mileage thing down and that we should have plenty left.
We pulled over immediately, tried to find the symbols in the manual and couldn’t, so pulled back in to traffic to try and find a better spot to stay at (we had 2 kids in the car. that’s not good for the shoulder of a two lane highway.). We made it into a large pulloff, and finally found in the manual that the hybrid system had shut off because of lack of gas. Of course, we’d run the battery almost dead. AAA came and towed the car. The shop charged us $150 to ‘reinitialize’ the system. I requested that they fill up the car with gas and tell me how much they put in there, because I was convinced there was a problem with the car (we couldn’t have really run out of gas because the milage on those last 3 gallons would have had to have sucked!). But, it was true. We’d run out of gas.
(The story actually is worse because we had the car towed to the nearest place in Eugene, which is two hours south of where we live in Portland. It was Sunday so we had to get a rental car to get home, then one of us had to take off work to get back down there to return the rental and get our car back. It was really about $300 worth of trouble.)
So today, it happened again. This time I knew what was up, pulled right off at the next exit and ended up just 1 1/2 blocks from the gas station. (If I’d realized that I might have tried to make it.) I decided to go get gas, put it in, and see what happened, since the battery still had juice. I was really hoping I wouldn’t have to have the car towed and pay to get it re-initialized again!
5 gallons later, I turned the car on and lights flashed and beeps came on, but the engine started and was recharging the battery. I left it going and tried to find more info in the manual… and about 5 minutes later, a few minutes after it had recharged the batter to about 6 bars, the crazy lights went off and it looked normal again. Whew!
Thanks for all the info.