Well, that experiment didn’t go very well

The Prius beeps and displays a large “Add Fuel” banner on the display. Vicki always starts looking for a gas station almost immediately after it beeps on her car. But with my older cars, I always knew how far I could go after the low fuel warning – on both of my Corollas, it was about 100 km or more. I never ran a car out of gas.

And so I decided to test it. I read on-line that the Prius tank is 12.5 gallons, but I’ve never put more than 9.6 gallons in it. So the last time the low fuel warning came on, I drove 50 miles before filling up. That got me 9.879 gallons. So this time, I figured I’d go 100 miles. After all, the display was showing that I was averaging 40 mph (it’s been really cold and my trip to work is too short for the car to warm up properly) so 11 gallons would be 440 miles, and the warning went off at around 325 miles, so it should have worked out.

So imagine my surprise when I was driving home tonight, and at 75 miles from the low fuel warning almost exactly, this big red warning icon came up on the dash, and the gas engine cut out. I quickly hit the “nearest gas station” button on the GPS, and put on the emergency flashers. I was able to drive on electric only for nearly a mile. Unfortunately the gas station was a mile and a half away. And these days, gas stations don’t carry gas cans. So I walked all that way for nothing.

Fortunately Vicki came to my rescue. Between the gas can and the fill up afterwards, I put in 9.92 gallons. While I was waiting for her, I googled and discovered that the Prius tank might be 12.5 gallons, it has a bladder inside that restricts the capacity to somewhere between 9 and 11 gallons, depending on the temperature. So I guess I was lucky to get nearly 10 out of it. And I guess I’ll start looking for gas 25-50 miles after the warning, rather than 75.

6 thoughts on “Well, that experiment didn’t go very well”

  1. Reminds me of the story of a guy who had an old VW Bug, from back before they had a fuel gauge. He never kept track of how many miles he’d driven since his last fill-up, because he’d gotten used to waiting until the engine began to complain and then reaching down under the driver’s seat to open the reserve tank.

    Until one day he reached down and discovered the valve was already open….

    (I may have first heard that story on a certain newsgroup. You never know.)

  2. I ran my pickup out of fuel a few weeks ago under similar circumstances – I knew I was low, but I didn’t think I was *that* low. Surprise. Thankfully I was rescued by a neighbor (it happened just around the corner from home) and the truck decided to actually start up again, something that doesn’t always happen with diesels because of the idiosyncrasies of the fuel system.

    Just curious – why were you only able to go about a mile on electric alone? I thought the Prius heavily relied on the electric side in urban situations, so I would have thought it could go a further without the support of the engine.

  3. Mark, I was on a controlled access road with a 55 mph speed limit and I was climbing off a bridge at the time, so I was probably driving too fast. True to my pilot training, though, the first thing I did was try to shed some electrical load by turning off the defogger, radio and head lights.

    If I was on a slower road or a down grade, I probably could have made it.

  4. the Prius tank might be 12.5 gallons, it has a bladder inside that restricts the capacity to somewhere between 9 and 11 gallons, depending on the temperature

    What the hell is the point of that? I gather it expands to pressurize the tank – why? To eliminate gas space? To put the fuel under pressure? What’s the point?

    Sounds (a) ridiculously counterproductive (how do you manage fuel if you can’t even know how big your gas tank is?), and (b) dangerous, or, what’s almost as bad, a kludgy fix for something that’s dangerous.

  5. Bladder tanks are not uncommon in situations where fuel leakage after a crash is of concern. Considering the high voltages running through the Prius electrical system perhaps it’s an extra safety measure.

    I remember reading an article a few years ago about special training that first-responder teams have had to take now to deal with hybrid automobiles due to these voltages. Add high voltage, possible sparking because of the accident and or rescue efforts, and leaking fuel, and I can see the justification for a tank bladder.

    Think Ford Pinto, if you are familiar with that whole infamous situation.

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