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How accurate are gas pumps- are you getting hosed?


Not even close. According to the above quote, shrinkage is more than 50% in 15 degrees of temp? Not water, not alcohol, not even any kinds of reactive vapor will shrink that much in a 15 degree temperature change. Alcohol is the only common liquid that will evaporate with that much change, but non-industrial liquids will NOT condense that much in such a small temperature change.
80 degree fuel would maybe evaporate some, but I don't believe it will lose even that much. 50% evaporation would make an extreme danger of explosion near any gas station.

Think the other way around. According to what Danger Ranger said, it would be doing the opposite of evaporation would do (It would get bigger at a a higher temp).
 
One thing is after the pump kicks off the hose is still full of fuel under pressure, so if you flip the lever to shut the pump off you can get a tad more (maybe a cup) out of it, but I figure I payed for it so I do it. Usually with my F-150 between the fuel gauge level and the pump I can guess to within a gallon of how much I am going to need to fill it up, so at least the ones in my area are pretty accurate. My Ranger is a crapshoot during the winter when I have the hubs locked in, I can drive around on empty for weeks (I only drive it on weekends) until I get paranoid and fill it up, and put a whole 9 gallons in, gotta love old fuel gauges. When running unlocked I just keep track of the miles.

Actually when my dad was in jr high, one of his classmates would go around to all the gas stations with his moped and get gas from the pressure in the hose (since not many people know about it) to fill up his tiny tank for free.

Hey how about the old analog gas pumps, yes there still is a station around here that has the old analog meters on their pumps, makes it hard to get exact(the clerk has the digital reading) but thanks for the tip!!:icon_hornsup:
 
Spilling out the filler neck is caused by AIR expansion in the tank not fuel. Actual fuel volume expansion is under single digit percentile.
 
20 gallons of 80deg fuel is only 9 gallons once the fuel has cooled to 65deg or lower

Maybe he missed an 1 on the 9 part. But still, wow if thats true.

A little FYI. The fuel pumps always round up. Ever notice the price, $3.079. So even if you but in exactly 1 gallon, you will be charged .01 more for a total of $3.08, not $3.07. But it only does this on every fill up, not every gallon put in.
 
Maybe he missed an 1 on the 9 part. But still, wow if thats true.

No, he's just full of voluminous white-hot flaming BS.

The coefficient of volumetric expansion for gasoline is barely 0.1%/deg C. This means 20 gallons at 80 deg F is about 0.7% lower at 65 deg F, or about 19.9 gallons.

You would think someone would GRAB AN FN CALCULATOR before posting such crap.

And of course the fuel is METERED into the engine according to the air it is ingesting. At part throttle, the fuel used is just how much BY WEIGHT is needed; the difference in volume goes away (weight is not changed by temperature).
 

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