I tend to fill my cars until the fuel is at the very top of the filler tube. I feel that I get a more accurate fuel mileage reading if I do it this way.

My reasoning for this is:

I am far from an expert on gasoline, but I will include a link to an article on “How stuff works” that (I think) tells you more than you ever wanted to know about gasoline. So the following explaination is in my own words.

Every time a person fills up their car, the fuel will have a different vapor property, in other words, its’ tendency to turn to vapor and shut-off on the nozzle. This willingness to vaporize is dependent on the formulation of the gas, temperature, region of the US, octane content, etc..

Anyway, when I fill the car all the way to the top of the filler tube, I am at least assuring myself that the “fill point” of my tank is at the same place on each fill up and so I can calculate my mileage based on what I believe to be an accurate calculation of fuel used.

I also start the fuel in at the lowest auto setting on the nozzle to allow the fuel “gases” to escape and not “bubble” the fuel too much.

I feel that I would get wildly varying mileage readings if I stopped putting in fuel when the pump shut off. There is a person on this board who is complaining about only getting 150 to 200 miles per tank of gas with their Fit. I’m wondering if they are sticking in the nozzle, turning it on full blast, then stopping when the pump turns off the first time.

If the fuel is very vaporous then they may only be getting 3 or 4 gallons in the car at a time!

I have had times when I’ve started to put gas in my car (during the summer) and have started the nozzle at full only to have it turn off in less than a gallon of fuel being dispensed! So to my mind I would not get an accurate reading of what my car is capable of holding (and fuel burned) unless I controlled where it was filled up to.

After doing this type of fill up about 4 times I know that I can figure on 36 mpg from the car or a range of 400 miles per tank.

As an aside, I have done this type of fill-up continuously with my Dodge Neon that I’ve had for 14 years without any problems with the vapor canister. Of course, as the saying goes, “Your results may vary. ” I only put this out as a commentary and my observations.

Thank you.
Link to Gasoline FAQ - Part 1 of 4

http://www.howstuffworks.com/framed.htm?parent=gasoline.htm&url=http://www.faqs.org/faqs/autos/gasoline-faq/part1/

 

I always fill to the very top as well. In fact I choose my fillup location based on how easy it is to do that. A few stations here have wide open flow or nothing. I visited Nashville last year and the station I stopped at only allowed an additional gallon to be added. The Fit has a very long filler tube. It ususally clicks off at about 7.5 to 7.8 gallons and I can easily fill it to 10+ gallons if I continue slowly from there.

 

If that were true, then i would only need to fill about 3~4 gallons at the pump each time...

=P

when i said i was getting 150 to the tank, i was meaning a tank of about 10.2 gallons total, that's what the readout on gallons the pump says, and that's what i know it put in there, when i go to the pump to refuel, i note the miles i drove, and i note how many gallons i just put into the tank and i divide... then i reset the counter on my dash.

=P

I'm always filling up when it needs to (the orange light) and it's always about 10 gallons.

 

Okay... so I'm reading a lot about folks putting in 1.5-2.0 gallons extra after it clicks at the fuel pump - saying that the filler tube is holding that much gasoline. How could this be possible? Those folks must be filling up the evap canister or something else... but not the filler tube. Here's why:

Here's my calculations:
1 US gallon = 231 cubic inches
radius = 0.5*(diameter)
Volume of a cylinder = pi*(radius^2)*(length of cylinder)

To get 1 extra gallon, Diameter vs. length of filler tube:
Diameter Tube Length
1.00" 24' 6" = 1 US Gallon
1.25" 15' 7" = 1 US Gallon
1.5" 10' 11" = 1 US Gallon
1.75" 8' 0" = 1 US Gallon
2.00" 6' 2" = 1 US Gallon

Looking at the filler tube, it only looks to be 1" or 1.25" in diameter. So the filler tube would have to be 15 to 24 feet long to hold 1 gallon. I know the filler tube is long... but not THAT long.

My question is... where is the 1.5-2.0 gallons of fuel going?
Why not just stop filling when the pump 'clicks'?

 

I took my Fit into the dealer for its first Oil change and I got to talking with someone in parts. I told him when I fill up I put more then 10.8 in the tank I get about another gallon of gas in the tank and neck. He told me this isn't a good idea but when I do this I get 340 miles between fill ups. is it ok are is the parts guy right?

 

Check out these articles. Both are very similar.
EPA.gov - Don't Top Off Your Gas Tank!
Do You Make This Mistake at The Gas Pump? by Scott Siegel Intergalactic Products LLC

Here is another article with a different perspective.
Car Talk - August 1999

There is no point to put that much fuel in your tank. I pump fuel until the nozzle clicks and I can get at least 320 miles out of it, but there is no reason for me to go that low either.

 

I call shenanigans. The only reason it is advised not to top of your tank is because the likely hood of a spill increases. Spills are the gas stations responsiblity and millions of dollars each year are spent on these cleanups. If a gas stations underground storage tanks are properly registered it acts like insurance where state and federal agencies foot the bill for these cleanups. If you pay attention to what you are doing and don't spray gas everywhere there is no problem.

 

I generally fill it up until it clicks, then pause and repeat 2 times. normally i fill up at the same station (and pump if possible) as my commute allows this without much issue. I figure if i do the same process then my MPG calculations should be more reliable.

I haven't viewed the tube setup, but it may get larger as it heads down to the tank or so on. As for the pump clicking off then fitting in 1.5 to 2 gallons I wouldn't doubt it, but I do doubt thats all being held in the tube.

I have had some pumps click off quickly (when my fuel light was on in this and other cars) at times because it was filling the tube quicker than it could drain into the tank. I never use a "full blast" setting on the pump. Normally somewhere in the middle range.

If you factor in the fuel held in the fuel system (lines and filter and so on ) filling with more than the tank capacity is pretty easy if you run it almost out. I try not to go to far after the light comes on myself. So far the most I have put in is 9.8 using the method above. I cant see any fuel in the tube, but i am also not trying to max out my miles per fill up.

 

I was just discussing this in another thread. There are a few reasons why filling up the tank to the very top is bad. Plus I just don't understand why people do it. I stop at the initial click which is usually around 9.8 US Gallons and I get AT LEAST 300 miles out of it when it hits 'E', which means there is roughly 1+ US Gallons left. Getting that extra gallon by filling the neck is only going to get you around 30 miles more, if that. IMO it isn't worth damaging your vehicle or the pump for 30 more miles.

 

I have only filled up mine twice so far but both times were at the same station and the same pump, just by luck. However both times I stopped after the first click. Then let the gas settle for a few seconds so all the bubbles have a chance to go away. Then top off to the nearest whole amount. For instance from 24.92 to 25.00 or 24.51 to 24.60. Just to make it a more even number for simplicities sake.

 

At one click the tank is not full, that is your answer. Gas foams a lot when you are fueling. Hondas are the worst for aiding the foaming. Generally Hondas and especially fits have several turns in the tube. When filling my Subaru, the click and about another half gallon and you could see a static fuel level. On the Fit Click and about another 1.5 gals and I can see a static fuel level. Is there a magic fuel tube or a bunch of lying fit owners I doubt it. Generally vapors go up and liquids go down, so I imagine the vapor canister uses these principles in its function. I have always filled completely to the top and have never even had a check engine light related to fuel vapors.

 

Same here. The fact that the free tankfull from the dealer when I picked up my car has never been equaled in my use of it since then, suggests that the average pump's automatic shut-off occurs before complete filling. Maybe the filler tube and tank are not all metal, but are instead made of a plastic or polymeric material that stretches?? Anyway, if I can get another .5-to-1 extra gallon in there after the first shut-off, I don't see any reason not to, and have not had any adverse consequences.

Further, gas pumps must have a very wide variance in the back-pressure necessary to shut the pump off. Simply trusting the first shut off as being "Full" will obviously give you erroneous fuel economy calculations. If, in any way, you can get more fuel in the tank after the first shut-off, then it was NOT FULL at the first shut-off.

The posted warnings on the pumps against topping off are to prevent over-filling and gas spills on the pavement, which would contribute to air pollution and fire danger.

 

What damage could you possibly do to your car as long as you don't run it all over the paint? I mean as long as it doesn't spill over, how could it be too much? Clearly not necessary, but damaging? To what?

 

Also, the gas is very cool while in the underground tanks. After you pump it into your tank, it will warm up a bit (and expand as a result), so if you top it off and then just park the car w/o burning some of the fuel first, it may expand and overflow. I top mine off when I'm going on a road trip and the car will not be parked between fill up and interstate cruising. Generally, i don't top it off.

 

My belief is that no damage is possible. So far, this has proven to be the case.

 

Similar is right; they're identical. Who plagiarized who?

 

Do fuel pumps even give an accurate measurement when you're topping off your tank?

 

There was in interesting thread about this on gassavers.org not to long ago, check it out here.