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Discussion Starter #1
How does one run out of gas with under the following situation.

12 Gallon Tank
48.2 Ave. miles (on this tank)
488 miles on the tank

Believe it or not in happened to me. I limped into the gas station on stealth mode (wow did the battery bars drop fast when your caught on the freeway, as I was), and filled up the tank which took exactly 11 gallons. I'm not a math major but something is not jiving. It would appear I'm not getting the mileage that the computer is calculating or I got an 11 gallon tank or @#$? Thoughts?
 

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This is an easy one... You started with half a tank.

More than likely the pump shut off early, and left you a few gallons shy of a tank full.
 

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Remember also that the speed at wich you fillup can also affect the blattre (or is id bladder?). Anyway, the slower you fillup, the more time it has a chance to expand evenly. So when you are "full", you may not have 11.9 gallons in the 11.9 gallon tank.

When the last fuel light blinks, I fill up at the first station I pass. Normally I try to fill up at the last fuel light BEFORE it blinks.

And yes, the average MPG on the display is not 100% accurate.
 

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Discussion Starter #4
The gas tank was full at the last fill up (not that easy my friend) and I always set the gas fill at the slowest rate. It took more gas than it has before at this fill, 11 gallons.
My car is just a month old and I had checked the VIN numbers relative to the service bulletins and it does not fall within the ranges of the cars that toyota lists as potentially problematic. So one or some combo of the following would have to be the cause:

> Actual capacity of the tank is less than 12 gallons (perhaps do to this bladder deal)
> The car wrongly thought it was out of gas and the computer just shut off the gas engine.
> MPG calculator is off.

Regardless, my assumption that I could computationally determine when I needed to fill (12 G x 48.2 = 578miles - buffer 50 M = 528) was wrong and I wanted to provide a heads up to anyone else who might be trying the same.
 

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ssutter2001 said:
Regardless, my assumption that I could computationally determine when I needed to fill (12 G x 48.2 = 578miles - buffer 50 M = 528) was wrong and I wanted to provide a heads up to anyone else who might be trying the same.
I wouldn't say your assumption was wrong, you just need to start with known figure. Base your assumption on the amount of fuel poured into the tank, and not the tank's size...
 

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11.9 gals

The same thing happened to me. I was on the freeway trying to get to blythe. I thought I could make it. 11.9X45MPG=535.5. I would be at 498 when I got there. The last 98 miles I had two bars, then one, then blinking for ten miles when all the warning lights came on at 494mi. I was also able to limp to the next gas station. I was only able to put in 11.2gal. I had to pay $2.39 gal. Three more miles and it would have been $1.91. I only have 4 tanks on this car. I went 53 miles on the last blinking bar and put in 11.4gals. I have read many other stories like this. I like your idea that when the car "thinks" your out of gas thats it, your done. I was going up a long hill when it happened. I thought maybe the gas moved to the back and the gauge read 0 so the car shut down to protect itself. But then was unable to reset itself when the car leveled out.
I also love how people are so quick to tell you "nope, you ran out of gas, no other reason" without being there. I very well may have ran out of gas but there could have been other factors as well.
 

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You both report getting about 11 gallons in after running dry. Ergo, your tank capacity is 11 gallons, not 12.

Tucsondave: substitute 11.2 for 11.9 in your formula, and your actual distance travelled is within a reasonable error margin of your calculated range.

Ssutter: It sure sounds like you actually had only 10 gallons in the tank. Or the MFD mpg is off. There has been discussion about this before, and some folks have reported inaccurate readouts.

The bladder is said to stretch with use. In a new car it may very well hold less than the stated capacity of the tank.

And what other car on the road would let you drive 2 or 3 more miles after you run out of gas? Only a Prius! Cool car.

Oh, and Dave, if you were concerned about the price of gas, why didn't you just buy one gallon of the expensive gas, and then drive on to the cheaper station? You could have had some fun with the attendant: "Sorry I'm only buying a gallon, but that's all this car holds. I sure wish it held more. I only made it 494 miles on this tankful."
 

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Variance between MFD and Pump

I setup my spreadsheet to keep track of the variance between fill-up and mfd and after 12 tanks

The MFD has indicated lower fuel use 8 times, once by as much as .9 gal.
The MFD has indicated higher fuel use 4 times, once by as much as .5 gal.

The average error is .22 gallons more fuel added to tank then MFD indicates as used. This is roughly 2.8%
 

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I was hoping the extra 6 dollars would teach me a lesson.
how can you say I have an 11 gal tank? I put in 11.4 gal before I left and was not out of gas then. Oh well, maybe I'll start getting gas at 310mi like my last car, just to be safe. 5.5 gals every 5 days is fun. :D
 

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tucsondave said:
I was hoping the extra 6 dollars would teach me a lesson.
how can you say I have an 11 gal tank? I put in 11.4 gal before I left and was not out of gas then. Oh well, maybe I'll start getting gas at 310mi like my last car, just to be safe. 5.5 gals every 5 days is fun. :D
I was approximating. You expected 11.9 gallons, but after running dry and limping into a gas station you only got 11.2 gallons in. Closer to 11 than to 12. That you had put 11.4 gallons in is information you had not previously given us. Sounds to me like bladder variability.

Either way, it's not a good idea to try to push to the limit. A good rule is, fill up as soon as the last bar starts to blink if you are in an area where you know where gas stations are. Otherwise (as on a road trip) calculate very conservatively and fill up sooner. People are running out of gas in pursuit of bragging rights regarding how far they got on a tank.
 

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tucsondave said:
how can you say I have an 11 gal tank? I put in 11.4 gal before I left and was not out of gas then. Oh well, maybe I'll start getting gas at 310mi like my last car, just to be safe. 5.5 gals every 5 days is fun. :D
But, as the manual notes, because of the bladder, the actual capacity can vary from tank to tank. It apparently depends quite strongly on the temperature. I remember them saying the capacity was like 1 gallon less at some low temperature...and the temperature wasn't even that low. (My manual's out in the car and I am too lazy to get it and give you the actual figures.)

melgish said:
The average error is .22 gallons more fuel added to tank then MFD indicates as used. This is roughly 2.8%
That sounds incredibly close to what I am finding. After 2700 miles, I am running about 1.4 MPG higher by the screen than by the gas station filler pump, which works out to your 2.8%. I also did an analysis of John's data (which he is kind enough to provide on his website) over the almost 20,000 that he's driven his 2004 and he was also running about 3% high. Strange that they all seem so close...I had heard that the screen MPG was accurate to about 3% and it was suspected that Toyota chose the numbers so it would be biased high...But, if we draw any conclusions based on these 3 cars (which is a little dicey, I admit!) the variance may be less than 3% but the bias right around 3%.

For what it's worth, I also looked at the data from John's 2001 Prius that he accumulated almost 60,000 miles on and there the bias was close to 5% high.
 

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3% Bias

That is an interesting observation. So either the calculation regarding the amount of gas injected relating to "on time" of the injector is off or the odometer is off. Has anyone checked their odometer accuracy at a calibration center? If not I will have mine checked when time permits and post the results. If THAT is the error then perhaps the "tire calibration" can solve this issue. Otherwise the resolution may be buried deep in the diagnostic screens. If it is not adjustable then the problem will vary as the injectors’ age.
Jim
 

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I have checked my odometer against the mile posts on the highway. With tires at 42/40 I was travelling approximately 1% farther than the odo indicated, assuming the mile posts were correct., which I imagine they are.
 

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Well, my tires were at 40/42 (doh! I fixed that today) so I should see less of a difference, not more right?
 

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Daniel said:
I have checked my odometer against the mile posts on the highway.
There's a thought... will have to try that on my next long trip. I'm guessing that I should note the trip odo (in tenths) at the first marker, and compare it to the last marker before I exit; heh, for that matter, I could reset "Trip B" as I reach the first one. :)
 

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Running out of gas

:shock: Running out of gas is bad for the fuel pump. In most cars the fuel pump is located in the fuel tank. The reason this is done is that the fuel pump uses the fuel in the gas tank to cool it's self. So when you run out of gas you could cause the fuel pump to over heat, and get damaged. It's most certain that repeatedly running out of gas will shorten the life of the fuel pump.
 

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Out of Gas

Also, when you run out of gas, the fuel pick-up sucks up the junk in the bottom of the tank, which can clog the fuel filter and injectors.
 
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