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I found on my 2005 Prius that the gas nozzle will shut off about 2 gallons before the 11.9 gallons is reached. If I very slowly fill after that so the nozzle doesn't shut off, I can get the additional 2 gallons in the tank. There is a danger of sometimes over filling and spilling a small amount. Has anyone else noticed this? Does pressure build up in the bladder tank that causes the nozzle to shut off? Did I see a post that the fill tube has been "made more flexible" recently? Was this the reason?
 

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You shouldn't top off. If you do, you are likely only pumping overflow gas back into the pump nozzle's vapor return lines. Ultimately, that gas gets put into somebody else's car.

:shock:

It's your money, though.

But if you do spill any gas, you're causing pollution. Why would you CHOOSE to do such a thing?
 

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I find I can add a gallon after initial shutoff, with no spillage. Two gallons would be pushing it. However, everyone's cars seem to be different in this respect, so find out what yours does and stick with it.
 

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I can safely fit an extra 1/2 gallon into my glove compartment in Ziploc baggies.......I figure if i'm in a bind....this will help me get at least another 25 miles +/-

- thinking about hollowing out my head-rest to see how much will fit in each!
 

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I did a test and filled my tank to the brink... 565 miles

Filled until the initial 'click' and pump shut off... 487 miles

Filled up to the brink again, and 'burped' the tank... 518 miles



Results: Topping off the tank works for meeeee



I have done a good handfull of times now and no spillage. I found out that once you get the sound and 'burping' down you can prevent spillage.
 

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No vapor-return here. However, to spend the extra minutes topping off in a time of shortages, one should plan ahead. If there's a line, somebody might get annoyed. Better to try again later than risk an incident...
 

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Do *NOT* top off the tank.

That intentional act of filling the vapor recovery system with liquid gas will contaminate the sensor there, exposing it to far more gas than it was ever designed to deal with.

Eventually, that will trigger an error code which cannot be shut off. You'll have to pay to have the sensor replaced (unless it fails before the 36,000 mile warranty expires).

You're also preventing the evaporative emission system from doing its job.
 

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john1701a said:
Do *NOT* top off the tank.

That intentional act of filling the vapor recovery system with liquid gas will contaminate the sensor there, exposing it to far more gas than it was ever designed to deal with.

Eventually, that will trigger an error code which cannot be shut off. You'll have to pay to have the sensor replaced (unless it fails before the 36,000 mile warranty expires).

You're also preventing the evaporative emission system from doing its job.
That means:
You will never know how much gas you are having in the tank to make the mpg calculation per tank or per intervales.
Then you do it per amount of miles and purchased gallons only. But even like that will be erroneous. Let's say you run 100 miles and the valve shut off with only one galon purchased.

YOU WILL NEVER KNOW THE MPG ACCURATELY IN THE PRIUS.
WHY...? Because if know it and compared against the sticker you will convince yourself that you got a car that needs some homework from you that was not specifyied prior the your purchase:
1.- AC off in all seasons.
2.- Heating off in all seasons.
3.- Pulse and Glide Summa Cum Laude Diploma given by Toyota Prius International University.
4.- A lot of Mazoquisim to handle 1, 2, and 3.
 

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bshef said:
I can safely fit an extra 1/2 gallon into my glove compartment in Ziploc baggies.......I figure if i'm in a bind....this will help me get at least another 25 miles +/-

- thinking about hollowing out my head-rest to see how much will fit in each!
I'm gonna waterproof the console twixt the 2 front seats. That will make an ideal spare gas tank. And as an added bonus, I won't have to deal with the added weight of passengers 'cause no one will want to ride in that gas-smell machine.

miles-per-tank rule!
 

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Seven7 said:
Results: Topping off the tank works for meeeee

I have done a good handfull of times now and no spillage. I found out that once you get the sound and 'burping' down you can prevent spillage.
What is your definition of "work". What does it do... Also, spillage is not puddle of gas on ground, it is gas in vapor recovery system or canister. I am not saying don't do it, I am saying, be intelligent about your assumptions.
 

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I too am a bit confused about topping off the tank. BIF says that if you keep holding the nozzle the gas will recirculate to the gas station, thus paying for gas you don't get. But John1701a says that it will fill the vapor recovery tank in the car and hurt an important sensor. Maybe it will do both, I don't know.

But I'm wondering, if BIF's statement is true then how much money could you pay pumping gas back to the gas station?

And how could just gradually filling the tank so it holds the full amount hurt the car as John1701a says can happen?
 

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Don't top off!

Overfilling is not a good idea on any car, but especially
so in a Prius with a bladder tank. The bladder has been known to belch
up excess gas "squeezed" into it on a slow fill, which is not good for
your now gasoline-soaked clothing, the paint on the car where the spill
was, and the large amount of unburnt hydrocarbons you just released into
the air. (Driving a 2004 Prius for 24,000 miles produces fewer smog-forming
emissions than spilling 1 cup of unleaded gasoline, so says a Toyota
brochure.)

Also, filling the filler tube full of gasoline will usually fill any
car's charcoal canister (part of the emissions/vapor recovery system),
overloading it and possibly poisoning it, such that your check engine
light will go off, which is the least of your troubles...

Some articles:
http://www.patgosscarworld.com/donttop.htm
http://www.phillyburbs.com/pb-dyn/news/ ... 23947.html
http://enviro2.blr.com/display.cfm/id/48985
http://www.sbcapcd.org/edu/dont-top-off.htm
http://www.weights.az.gov/Shoppers/gasstations.htm


and as for figuring out your fuel economy - best bet is to use the same gas station/pump all the time (same shutoff), and to average several tanks rather than just one particular tank at a time. It's not uncommon to get a really low fuel economy tank followed by a really high fuel economy tank...
 

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I don't top off...never have for any of my cars, past or present. I have, however, noticed a large difference in the mileage I get depending on whether or not I squeeze in an extra gallon after shut-off.

For example, the two times that I've gotten the extra gallon in, I've gone over 110 miles before the first bar on my gauge disappears. The times when I've stopped pumping immediately at shut-off (about 8 gallons), I've never gone more than 50 miles before the first bar drops.

Now, I know how everyone says don't overfill because of the bladder and the vapor/emissions deal, but that extra gallon makes a big difference.
 

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but that extra gallon makes a big difference.
While I can see the difference in the number of miles you can drive, I have a hard time seeing how this makes a big difference in anyones overall life. With a ten percent increase in range that means that if you fill up your car every 10 days without adding the extra gallon, you could go 11 days with topping off. Woo Hoo! Is this really an improvement in anyones quality of life. I have had cars that can only go 250 miles or so on a tank of gas and the Prius, not topped off, exceeds the range on any car I have ever had. Doesn't seem worth the risk to me.
 

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Re: Don't top off!

mrv said:
Overfilling is not a good idea on any car, but especially
so in a Prius with a bladder tank. The bladder has been known to belch
up excess gas "squeezed" into it on a slow fill, which is not good for
your now gasoline-soaked clothing, the paint on the car where the spill
was, and the large amount of unburnt hydrocarbons you just released into
the air
I never add gas after the automatic shut-off, but on my last fill-up, it burped an ounce of fuel all over the side of the car as it shut off. Since I had just detailed my car, and put one coat of Klasse All-In-One, three coats of Klasse Sealant Glaze, and one coat of Four Star Ultimate Paint Protector on it, I was real happy to have to go home and redo the area under the gas flap. Grrrr.
 

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You do not have to top-off the tank to get an accurate mpg reading. In fact you only have to fill it up to almost full twice to get an accurate long-term mpg figure.

Fill up your tank at the beginning of your mpg test, stop when the pump clicks off.
During then test period refuel with any amout that you wish, you can fill the tank or not, it does not matter. Record the amount of gallons.
At the end of the test (thousands of miles later) fill the tank untill the pump clicks off.
You may not have exactly the same amount of fuel that you did at the beginning of the test but it will be a small error. If your test period is 5000 miles you will have pumped in about 100 gallons, an error of 1 gallon is only one percent.

Roger
 

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That's good for long term MPG, but it doesn't help when you are looking for trends. But then that's what the MFD is for.
But I still find the MFD more optimistic than calculated, but that difference seems to vary quite a bit.

To prevent spills, remove the nozzle every .1-.2 gallons. If you see gas stay at the neck, or is slow to go down, STOP!

Click-off has been known to be premature, especially with all the tight fittings and the bladder. Perhaps what might help some to stop topping off is a technical description on how the pumps determine the tank is full. Also the vapor recovery supposedly pumps have should be described. I suspect the nozzle output is greater than what the vapor recovery could take in in liquid fuel, if indeed it can even take any. Thus if you were overfull, you'd be spilling.
 

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hyperion said:
Is there anyone who believes there is an adult car owner that doesn't know how to put gas into a car?
I'm not certain my mother can. We're in NJ, where we don't pump. Not convinced she could.
 

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hyperion said:
Is there anyone who believes there is an adult car owner that doesn't know how to put gas into a car?
I'm not certain my mother can. We're in NJ, where we don't pump. Not convinced she could.



But you live as do others in New Jersey and you know how. Your mother might surprise you. Even if you have never done it before, it really takes little intelligence.
 
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