[seaprius]

howdy folks!!!

Today was my fourth trip to the gas station since I got my 05 black prius. I fill up the gas tank when the last bar on the fuel indicator starts blinking (I drive about 20 miles after the blink starts). I noticed that I can't fill up above 9gallons. So, what is the max tank capacity? Is 9gallons normal? I have #4 package!

Thanks!!!

 

[An04Prius]

howdy folks!!!

Today was my fourth trip to the gas station since I got my 05 black prius. I fill up the gas tank when the last bar on the fuel indicator starts blinking (I drive about 20 miles after the blink starts). I noticed that I can't fill up above 9gallons. So, what is the max tank capacity? Is 9gallons normal? I have #4 package!

Thanks!!!

You will likely find that when the last pip blinks, you will pump anywhere from 7-10 gals depending on a whole bunch of variables (including how long you drive after it starts flashing), which I dont pay much attention to. The tank holds 11.9 gal according to the manual.

When the light flashes, get gas :wink: , works for me.

 

[Tideland Prius]

That's about the max I've put in the tank in one go. But then again, I daren't test the limit of the blinking light and also I tend to fill up a bit earlier (around 1 or 2 bars) when the price drops

 

[Astrowoman]

I fill shortly after it drops to 1 pip. Usually around 9g. The manual says a quarter of a tank is a good time to refill and that's what I learned early on, too... Why do Prius drivers have such a mania with waiting til the last minute? Are we being evironmentally responsible by limiting the emissions associated with fueling? Or are we just obsessive by nature?

 

[hyperion]

As long as you are driving a car made to sell in the US with the bladder you are not causing any emission problem when filling. Thats the object of the bladder and should eliminate all critism of it.

 

[Astrowoman]

That's an interesting point, but there is always a bit that escapes or even dribbles when the nozzle is removed, even here where the pumps often have a vapor recovery system as well...

So, you're saying we're obsessive, then? :wink:

 

[MarkWilliams]

Obsessive?? NAH! :shock:

(Now, WHERE did I put my lifetime milage chart?) :wink:

 

[Roger V]

tank capacity

here is something to try: if the mfd indicates 50 mpg, and you have gone 500 miles, try to put 10 gallons in the tank. It may take a little time and effort, but you can slowly fill it and see if all the numbers match. I have done this, and have come within 2 or 3 tenths of a gallon to what the display says has been used. It is handy to have a pocket calculator if you don't have the easy math example mentioned above.

 

[DanMan32]

Are you saying you CAN'T put 10 gallons in? I would problably be able to put 10.3 gallons in, at least.

 

[Roger V]

Tank Capacity

DanMan,
No, what I was saying is to try to put the amount of gas in that the computer says you used, based on the same computer telling you what the average for the tankful just burned. As an example, on my last fill, the computer showed that I had averaged 60.1mpg for 545 miles. If you divide 545 by 60.1, it shows that 9.068 gals were used. (rounded off to match pump configuration) I was able to put 9.293 gals in the tank. Now, I probably got it slightly fuller than on the previous fill, or maybe the temp was slightly different, as the time was approximately 1 hour earlier in the afternoon. This gave me a calculated average of 58.6 mpg as opposed to the 60.1 shown on the mfd. (BTW, the last pip had been flashing for over 20 miles, apparently with at least 2 gals still in the tank.)
The best way to figure gas mileage I think is over an extended period of time, so that you allow for variations in temperatures, levelness of the driveway at the pump, how full you actually are getting the tank from time to time, etc.
You also have to be very careful when topping off, which is why all the pumps where I live warn against the practice. The Prius will sometimes make a gurgling sound, which I take to mean it is very near full. If gas sits in the top of the filler neck for more than a few seconds without draining down into the neck, I consider it full.
I apologize for the length of this posting, and hope it clears up what I was trying to say earlier.

 

[Astrowoman]

As a creature of habit, I tend to use the same pump at the same gas station all other things being equal. My calculated mileage is on average pretty darn close to what the MFD (you know, the one I've been resetting when I don't really need to...) indicates. Consistency is a virtue I surmise...

 

[DanMan32]

After 39 tanks, I have driven 22595 miles with 411.01 gallons used, that yields 55.0 miles per gallon. If I take the MFD readings for each tank, figure out the amount of gallons I should have filled, and added them up, MFD says I used 398.52 gallons, giving an MFD average of 56.7 miles per gallon. So, if I filled up using what the MFD told me, I would have an empty tank right now. Even if you add the benefit of .2 gallons for rounding, for 39 tanks that's 7.8 gallons, still 4.69 gallons short.

My MFD is high, I tell ya!

 

[Astrowoman]

DanMan, I don't disbelieve you, but on average that is really quite close... and I'm still not convinced that the pumps aren't less accurate than the fuel-injector based calculation.

 

[DanMan32]

True, hadn't factored the pumps being inaccurate, but that's an awful big inaccuracy: .32 gallons per tank for 39 tanks. That's like 3%!

 

[Astrowoman]

As the error is in favor of profit to the gas station, I remain skeptical. I wonder what the tolerance on gas pumps is supposed to be?

 

[sphillab]

I'm with Astrowoman on this one, especially given that 3% of a gallon is only 133.4 ml. I'd like to think that the pumps are deadly accurate, but you're talking about being short by only 113.4 ml. out of 37,800 ml. pumped in a 10 gallon fillup. Seems a very likely possibility to me, especially if you look at how little 113.4 ml. actually is.

Personally, I always use the MFD mileage calculation. At least with that calculation I'm measuring both miles traveled and gas consumed using the same machinery. If I calculate my mpg using the car's odometer and the gas pump's scale it seems to me that I'm introducing all sorts of variables that could contribute to measurement error.

 

[DanMan32]

Sorry sphillab, but you misscalculated. That would be 113.4 ml per gallon, or 1134 ml for 10 gallons. You changed loss per gallon to loss per tank. And remember, overall, I have had contunually been lossy. Yes, there were a few points where I underfilled a tank, but then had to overfill more next tank.

 

[sphillab]

Doh!!! I hate it when that happens! I guess it's back to grade school math for me...

1134 ml sure does seem like a substantial difference in fuel consumed between fillups. I still wonder, however, about all of the other variables that could influence differences in calculated versus MFD mpg.