How accurate are gas pumps- are you getting hosed?

[WildSide]

Everyone complains about the price of fuel at the pumps but how many trust the accuracy of the pumps?
Even though the pumps are calibrated can they be ‘fixed’?

To what percentage is your pump accurate to- and is it in your favor or the station’s?

And what about volume correction methods?

How many have actually physically measured a gallon or liter of gas, LPG... just to check?

 

[97RangerXLT]

well, the way to test this theory out is to go get an empty 1 gallon gas can. weigh the can. fill it up to exactly 1 gallon on the fuel pump's meter.

weigh the now full gallon container and subtract the empty weight. The typical weight of gasoline at 72 degrees F is around 6.25 lbs per gallon, so if your gas can is significantly lighter, you are looking at some calibration or fraud issues.

Something to remember, gas as it comes out of the ground is going to be colder than 72 degrees, so it should be somewhat more dense and therefore a bit heavier than the 6.25 lbs.

Oh, make sure the scale you use to weigh the gas is a commercial style scale that is legal for use in trade and has been calibrated for the most accurate results

AJ

 

[97RangerXLT]

Another note on the gas stations, In IL they are inspected every year, so it is unlikely that they are going to be too far off. The gas station owners can face some hefty fines for running pumps that are way off calibration, and in all likelyhood closed down. Plus, how many people are going to visit that gas station or even the chain that the station belongs to if a news story breaks about their pumps not being accurate? Way too much risk for the station for that to happen knowingly.

AJ

 

[WildSide]

Yes all pumps are inspected and the dates vary between inspections as well no pump is exact or perfect either so there has to be a tolerance. And do certain states use temperature volume correction?

 

[97RangerXLT]

i am sure they do use temp/volume correction. the weight of a gallon of gas at 65* (the temp it is likely to come out of the ground) is much heavier than the weight of a gallon of gas at 80*. the tanker truck that pumps it into the ground is going to be considerably warmer than when it cools off under ground, so if the station pays lets say $3.00 per gallon of gas that comes off the truck at 75* and charges the customer $3.25 for the gas that comes out of their tank at 65*, they are going to lose money.

I am sure if they are within a certain percentage of the weight/temp or vol/temp they will be fine. and it is probably slightly on the stations advantage, but for your fillup it won't be that much of difference, probably only a few pennies.

AJ

 

[Donnie strickland]

The Birmingham (AL) News ran an article on this in 2005.

In Alabama all pumps are inspected once a year. The gas is pumped into a vessel and then weighed, with the temperature noted. The state Commisioner of Agriculture and Industries, who oversees this process -- and occasionally participates in it -- said that finding a station out of compliance was very rare, and that if such a station was found, it was as likely to be out on the plus side, as the minus side.

 

[VaGent]

The state of Virginia is the same as Alabama in it inspections process. They are very strict on the weights & measures. As I used to work for an oil company at one time, part of my job duties where to pre-calibrate all the pumps so when the state inspector came around, there would be nothing wrong with the actual readings at the pump. The pumps are all computer comtrolled & if anything, the customer will in the majority of cases get a little more then what the pump actually states. But not by much.

 

[reno]

I know there have been a number of stations here in Florida over the years getting caught cheating. The Owners had installed electronic devices that would change the calibration in their favor. The fines? $150 and a stern warning each time. It took 5 times for one station to finally get shut down from selling any fuel anymore.

I would hope that the laws have changed here to prevent this from happening anymore. I almost believe the FL laws were wrote by criminals for criminals so times. I would love to get out of this state, and the wife and I have agreed that when her father passes, our home goes up for sale, and we are gone.

 

[85_Ranger4x4]

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.

 

[Redneckryder]

in michigan, if you call the dept of agriculture or whoever is in charge and complain about a station, they will come out and test that station. the news said they are constantly testing the pumps all year round.

 

[pillen140]

new york they test every year also, but at the same time, thefuel pumps themselves measure the temperature as you pump it. then pump the amount of fuel accordingly, no matter what.

 

[1987 DANGER RANGER]

20 gallons of 80deg fuel is only 9 gallons once the fuel has cooled to 65deg or lower

 

[kunar]

20 gallons of 80deg fuel is only 9 gallons once the fuel has cooled to 65deg or lower

so the next time i fill up in the morning, it will be spewing out the filler by noon?!?!

 

[dogboy]

My auto shop teacher ran a Cheveron station with a shop/ garage in it. He said they cam out and tested once and his pumps were outside of the limit of tolorance, but he was actually giving customers MORE gas than they were paying for. They still fined him anways since it was not correct.

EDIT: 87 Danger Ranger, sorry, but I am going to have to call bullshit on that statment... That does not seem right. If that were the case, then mine would have overflowed MANY times by now. And, people would be buying gas in the morning instead of the afternoon and I don't see that either.

 

[srteach]

20 gallons of 80deg fuel is only 9 gallons once the fuel has cooled to 65deg or lower

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.