Pass Gas Slowly
 

Is is really true that filling up slowly gives you more gasoline because doing it at the high rate makes foam, which means that there is more air mixed in with your gas?

No

No. Think about blowing bubbles in milk versus water. Bubbles in gasoline would go away too quickly to cause foam.

I have no idea, but thanks for the laugh with the clever title :)

Filling up at a higher rate causes the fuel to splash, which sometimes trips the sensor and shuts the pump off.

( Pull my finger )

No you will not get air mixed in your gas.
Like robbiewt said, it's more like blowing bubbles in watter, the bubbles will NOT last long.

but... as your filling the air that is in the tank needs to come out as the gas takes up the space. the air rushing out faster due to a fast fill can "Some times" in "Some cars" can cause some gas to get splashed back onto the fill nozzle. the pump will shut off thinking fuel is now up to the nozzle and shut off to prevent an over flow.

in the past I have had cars that if I did not place the nozzle in the fill tube at the right angle the air would catch some of the gas and shut off the pump to soon.
at some point you will have a pump shut off to soon and it's most always due to air rushing out.

to avoid that and get a fill to a consistent point each time I pump slow. less splashing = more consistent fill point = better ability to accurately calculate my FE.

Thanks! It's bean good learning :)

I've always pumped at the first auto-click in the handle, only to prevent loss of fuel from splashing and overflow.

The actual issue with pumping quickly (whether it's true or not, I suspect not) is not foaming, it's vaporization. The idea is that the faster you pump your gas, the more quickly it vaporizes, and the more of it you lose due to evaporation.

The idea is probably somewhat correct, but the time differential sets it off - If you take longer to pump, even though you're creating less vaporizing turbulence, you're giving the fuel more time to vent into open air.

If you pump faster, you're creating more fuel turbulence, which might vaporize more fuel, but you're giving the bulk of the fuel less air-time to vent.

It's probably a wash.

The other issue is that fuel pumps are certified with a margin of error, maybe +/- 1%... the pump is more likely to "break even" at a slower speed.

When you pump from a preset, most pumps now slow down when you get within about 1/2 gallon of that preset amount, so they don't cut off too soon or go over. Keeps you closer to being "on the dot".

Just avoid the problem entirely. My car has a 10-gallon tank. If I put the nozzle on its slowest setting, that gives me just enough time to wash the windows while it fills :-)

I always thought there was a vapor catch in the pump somewhere and it is designed to catch any vapor that may have come from the giant tank underground and recirculate it back into the tank, so that you don't get this bubble of air/vapor into your tank and have the pump count it as gas. I've noticed that I do get these bubbles out the nozzle when I pump at full speeds, so I put it on the lowest setting to allow it to trap all those vapors and get me more gas.

Plus, I get more time to get those bugs off the windshield! :thumbup:

I think there is a vapor filter in the tank, before the pump, but I can't verify that.

I've been burned enough times with pumps with a broken kickoff so I don't leave the nozzle unattended.

Mine will often kick off sooner if I pump faster. And pumps have such wide variations in speeds, so what I do is try to pump about .1 gallon per second, just imagine a clock ticking. That way I get the most consistent fill I can. I also make an educated guess as to what it's going to take to fill the tank, and listen for the gas to start gurgling as it gets full. That way if the kickoff is broken, I can avoid spillage. Sometimes it still fails me because some noisy vehicle will fire up as I am getting ready to finish.

man, I've never had that. But yea, I stand with my hand on the pump. Sometimes it pumps too fast on the lowest setting, so I pump manually. when I can hear air bubbles, or vapor bubbles I pump it slower till I hear a smooth liquid flow sound.

If the setting is right though, I'll put it on low, wash the windshield, and then come back to manually pump it to finish. Good thing about a big tank huh? :D

Your car starts without anyone in it? Creepy.

What?

Depends on the car and the pump. My regular gas stations don't tend to "spill over", so I let it fill until it stops, then wait 10 seconds, then remove and reinsert and give it one more "click." That way, I'm sure that it didn't click off 2 gallons too early. I pump slower at unfamiliar gas stations, as the Clunker tends to trip the pump too late and dribbles a little onto the paint.

I think he meant wagonman: :D

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I'll put it on the fastest setting, then when I know it's getting close to full (comparing gallons pumped vs. how empty my tank was) I'll pump slow till it clicks off, then pump slow till it clicks off again.

Just filled tonight, and it didn't shut off so I got topped off to the top and a little spilled. :mad:

Nah, mine aren't usually noisy and don't start on their own. Now if I had a remote start then it would probably happen sooner or later. I just meant somebody starts their noisy vehicle like the tons of pickups around here with loud pipes. Drowns out the noise of my gas tank approaching full.