Do NOT trust the gas pumps!

[Recumpence]

Hmm, what looks odd about this receipt for gas? Look closely. I am not talking about the difference between the car computer and the gas pump, I am talking about the fact that this car only holds a maximum of 13.5 gallons of gas........

 

Needless to say, I reported this station to the EPA for fraud........

 

Matt

[MtnMarty]

Somethings crazy?

[Recumpence]

Yup, that gas station has a bad pump, that is what is crazy...............

 

Matt

[SnitGTS]

It happens all the time, I live in NJ and used to work at a gas station, they got busted for the same thing.

 

Not many people get gas with a virtually empty tank where the pump being off 2.5% is that noticeable.

[Recumpence]

That is more than 2.5%. I used, at most, 13 gallons. But, the pump showed 14.1 gallons.

 

Matt

[SnitGTS]

I went from the maximum the car can hold, 13.5.

[Recumpence]

That would still be 4%, not 2.5%.

 

I do not mean to quibble, but that is quite a bit. How many gallons are pumped at that station per year? That is a HUGE amount of money stolen from us........

 

I will trust my car computer from now on.

 

Matt

[SnowStorm]

It must be the "hybrid tax"! ;)   Seriously, I wish there was a way to safely check a pump now that we are really getting into the finer points of fuel economy calculation.  It wouldn't surprise me to find the car computer being more accurate.

[salsaguy]

you didn't use the trick i suggested in another form. this will also save you money before you fill all the way on a bad pump:

 

when filling, fill to exactly exactly to 5.00 and also to 10.000 gallons  (you may need to go slower to stop in time).

 

at 5 and 10 gallons the pump should show a price that is exactly 5 and 10 times the current fuel price.

 

if it's not they have a bad pump or are cheating you and you should take a pix of the pump screen showing how much it's off and report it.

 

if the 5 and 10 gallon price is correct, it's safe to continue to fill it all the way.

 

This is the way the Bureau of Weights and Measures and NIST test pump accuracy

 

Edits:added 5 gal test and ref to WAM and NIST.

Edited June 12, 2013 by salsaguy

[Jus-A-CMax]

Hey Salsa, make this a thread by itself in this Fuel Mileage section and I'll pin it, Subject should be: How to check your gas station is in compliance or not. Or think of something short and meaningful.

 

:)

[Noah Harbinger]

you didn't use the trick i suggested in another form. this will also save you money before you fill all the way on a bad pump:

 

when filling, fill to exactly 10.000 gallons  (you may need to go slower to stop in time)

at 10 gallons the pump should show a price that is exactly 10 times the current fuel price.

 

if it's not they have a bad pump or are cheating you and you should take a pix of the pump screen showing how much it's off and report it.

 

if the 10 gallon price is correct, it's safe to continue to fill it all the way.

 

There's still some room for variation, as different pumps will shut off at different fill levels. If you go to the same station and use the same pump twice in a row, though, it should be true. 

[salsaguy]

in my trick you are controlling when to let go of the pump trigger to stop at 5.00 and 10.00 gallons to do the check, not when it clicks off

even if you get close you can still verify if the pump is on target or not

you could do this at 1.00 gallon as well but most devices are less accurate at the extreme low and high end of its range, but it still should work.

it's just a quick way to easily see seeit is doing the multiplication correctly or not.

Edited June 12, 2013 by salsaguy

[salsaguy]

some stories related to this topic and how to protect yourself from fraud:

 

http://m.youtube.com/#/watch?v=aKne0RTSUas&desktop_uri=%2Fwatch%3Fv%3DaKne0RTSUas

http://www.njconsumeraffairs.gov/press/gasstation.htm

http://www.caranddriver.com/features/the-pump-police-feature

http://www.ehow.com/facts_5684842_do-gas-pump-fraud-to_.html

 

of interest:

"The NIST shuts down any pumps that measure a difference greater than 3.3 ounces per every 5 gallons of gasoline."

 

of even more concern, and what kills my trick posted above:

"While many consumer complaints cannot be substantiated as a result of investigation, a significant number of complaints can be verified,and often uncover problems or fraudulent practices that are not found in routine inspections.  For example, California county and state weights and measures officials received several complaints about a few service stations for shortmeasure deliveries.  An extensive undercover investigation revealed that a few unscrupulous people were modifying the software for gasoline dispensers so that they would deliver shortmeasure for quantities other than at five and ten gallons, which were the points at which the inspectors normally test the accuracy of the dispensers.  In another instance, gasoline dispensers were programmed to deliver short-measure, but when the station attendant sawthe weights and measures inspector arrive to conduct an inspection, the attendant would turn the power off to the dispensers to reset jthe software and deactivate the fraudulent software until after the inspector left the station. "

 

taken from the PDF report I found on the NIST site

Edited June 12, 2013 by salsaguy

[hybridbear]

you didn't use the trick i suggested in another form. this will also save you money before you fill all the way on a bad pump:

 

when filling, fill to exactly exactly to 5.00 and also to 10.000 gallons  (you may need to go slower to stop in time).

 

at 5 and 10 gallons the pump should show a price that is exactly 5 and 10 times the current fuel price.

 

if it's not they have a bad pump or are cheating you and you should take a pix of the pump screen showing how much it's off and report it.

 

if the 5 and 10 gallon price is correct, it's safe to continue to fill it all the way.

 

This is the way the Bureau of Weights and Measures and NIST test pump accuracy

 

Edits:added 5 gal test and ref to WAM and NIST.

This only checks if the price is correct. I don't think that's the issue. The issue is that the gallons displayed on the pump are incorrect. That means that when the pump says 5.000 gallons it isn't really 5.000 gallons that have gone into the tank. That is what Matt experienced

[BIG ROCCO]

I read a story once that the weights and measures checks are made in the Boston area were at 5 and 10 gallon amounts, and the fraudulent stations made sure the pumps were accurate at those exact levels, but read high at any other levels.

 

Edit: I just went back a few posts and followed salsaguy's links - I see they mention and show the 5 gallon containers used. The interesting thing about the story I had read was that the pumps WERE accurate at 5 gallons - just not accurate at other amounts

Edited June 12, 2013 by BIG ROCCO

[subter]

There are several other valid reasons for this to occur such as this:

http://www.sciencedaily.com/releases/2005/10/051023120710.htm

 

Also, ambient temperature as gas expands/contracts.

[SnitGTS]

The pump will calculate the cost from the gallons it says it's delivering, so that trick won't help.  The only way to test the pumps is to get a 5 gallon container and fill it up to the 5 gallon marker and see what the pump says it's pumped.

 

I updated my fuelly to reflect the gas my car says it has used.

[salsaguy]

hard to believe they could make it read correctly at 5 and 10 but not at others, since it has to be mostly linear right???

but yes you have to weigh it to prove for sure, which is why it's best to stick with known name brands and active stations not a out in the boonies where no one goes.

[obob]

If I were testing a pump I would get a container,

put some gas in it, doesn't have to be 5 or 10 gallons,

then multiply the number of gallons by the density of gasoline

and then weigh the container with the gas and subtract out the weight of the container

and see if the numbers match.  

 

And then multiply the price per gallon by the number gallons to see of that comes out to the pump price.

 

( then pour it into my tank with the handy dandy funnel. )

[plus 3 golfer]

Hey Salsa, make this a thread by itself in this Fuel Mileage section and I'll pin it, Subject should be: How to check your gas station is in compliance or not. Or think of something short and meaningful.

 

:)

PINNED???  This whole thread ought to be deleted. ;) Unless one has a certified container, pumping gas into a container is a useless exercise to check the accuracy of a pump.   

[plus 3 golfer]

I updated my fuelly to reflect the gas my car says it has used.

You're kidding right?  

 

I think I'll correct mine for the fuel I think I would have used had I "hyper-miled". ;)  

 

Did you see the link above?  There are some diesel owner's (fuel tanks are usually the same as ones used on gas vehicles) that "vent" their tank.  Since diesel is not as volatile like gas, the "vapor" space is really not needed.  All that needs done is to let the air out of the vapor area when filling.  This can generally be done by removing a valve in the filler neck or by adding a line from the top of the tank (vapor space area) to near the top of the filler tube and the vapor space can then be filled easily. Just rocking the vehicle back and forth can allow air to be replaced by gas.  On VW TDIs, use of this vapor space can increase a nominal 14.5 gallon fuel tank by 3+ gallons.

 

Ever notice when filling that one can fill to the brim normally and then if one waits a while one can usually add more fuel. Where does the added fuel go - into the areas used for the EVAP system including the vapor space.