Fuel Pump Is Not Accurate

I just filled my jerrycan at a servo only to find out the fuel pump was not accurate at all, its about 5% less (fuel pump said already 30L but not quite in the jerrycan)! I only checked it after I went back home so I didn't told the lady working at the servo on the spot. I am not trying to make a complain either as basically I have no proof after I went back home. But then again, I don't think this is doing the community any good if this practice is not being reported. What can be done? Visit the servo next time and ask the staff to watch me fill the jerrycan? Or just report this to an authority (is there even one)?


    • Is that regular. Premium or ethanol?

      What if there is undisclosed ethanol?

  • +1

    The same with cars… “my car has a 55 litre fuel tank but I put 62 litres in it… fuel station is ripping us off…” right after they necked the fuel filler nozzle.

    Should only be filling the jerry can to the fill line and leaving room for expansion. And really, your scientific measuring container is a “jerry can”…

  • +2

    The alternative is to go to another service station and fill their 30 Litres and mark this point.

    The at least you will know which one locally gives you a better measure.

    If over time you do the same thing and mark the fills you have a better idea.

    Although depending on the composition of the jerry can (eg plastics based) the time of day and heat of the can before filling will give you more/less space in the can. So ideally the temperature should be the same at each fill.

  • +3

    Bet OP didn't know they were really asking a science question!

  • +18

    There is an authority. Its called the National Measurement Institute (NMI), and Department of Industry, Science, Energy and Resources (federal)

    They use specially calibrated stainless steel measuring cans with very accurate indictors on them to calibrate. It has to be done when commissioned and then re-done every so often, I can't remember which. All have to be calibrated periodically and after repairs etc. They put a tag on there to say who calibrated it and their license.

    It's all quite regulated.

    Small quanitities and stop/starting reduces accuracy.
    Weather / temp also effects volume.
    Your can is probably not that accurate.

    Most servos now also have electronic dip monitoring and leak detection systems. They then use sales data to data match the sales quantities with the deliveries so they can calculate any fuel losses. They like them to be accurate so they can check for leaks and avoid big $ problems.

    I doubt many people would have opportunity to intentionally rip customers off. You can get meter creep over time though.

    • +4

      This guy petrols

      • yeah, been there, done servos - in a past career detour

    • +1

      my brain was trying to remember the term for the dip monitoring and I just recalled it - Automatic Tank Gauging (ATG), often with automated variance control / wet stock management systems.
      They can even detect water levels in the bottom of the fuel tank automatically from density changes, correct for temperature correction etc.
      many even lightly pressurise the fuel lines and have meters that check for pressure losses across stationary lines when not in use - also to detect leaks.
      Some cool measurement instrumentation and systems go into a modern servo

    • -3

      I doubt it, say the pump is accurate at 1 litre, 2, 3, 5 which will pass the authority but what if over 20 litres or 30 litres? No one knows only the owner knows…

      • The manufacturer of the pump you mean?

        • the owner, not manufacturer.

          • @superuser: yeah no - that's not how it works.

            Bamboozle asked if you meant the manufacturer and rightly so… Most likely the owner has nothing to do with it at all. Even at an independent.

            • Most dispensers are Gilbarco Veeder Root in this country although there are some others and newer ones such as Wayne Fueling systems gaining popularity. You can't ring up and order a dodgy meter as some mysterious underworld "owner", they sell them globally and a fuel contractor installs them (or in many cases they came with the dispenser from new);
            • Contractors with NMI licenses come in and do the testing and fine tune the calibration;
            • They test 15L at a time to calibrate the meter, most likely more than once to check calibration, it remains in calibration as a NMI certified product by design as more is dispensed;
            • They tag it with a tag that breaks if tampered with. Inspections from authorities or future contractors would reveal this or even during a routine maintenance…

            Now add in that most owners are likely a multinational corporation that would suffer way more brand damage than it was worth if they were somehow passing on instructions down the chain to rip off customers (e.g. Caltex/Ampol, Shell, BP, Puma, Woolworths, etc etc) - the "owner" if there was even such a person in those organisations, would not be involved in tampering with calibrations.

  • Sounds like OP is inaccurate but wants to make the fuel pump look bad :D

    • +3

      Blame shifting behaviour is often exhibited on ozbargain forums.

      • Totally, Red herrings runs rife around here…

      • Don’t blame us!

  • +1

    I must say there was one petrol station in my town that always gave me huge bills, whenever I went there more fuel went in my car than at other places. Without needing proof I just avoided that petrol station. Bit sad as they were one of the few independents. Not only was the petrol a bit more expensive I'd typically need close to 60 litres to fill up whereas at other petrol stations it was typically closer to 55 litres for my 60 liter tank.

    Totally unscientific of course, but …

  • +2

    if it is a plastic jerry can, the expansion rate is different, I have 2 and one should hole 20L.

    When I go to a petrol station one filled with 21.5L another one filled with 20.5L both on the same line.

    I realised that the one fill more(older one) look more expanded compare to the new one.

    so if you go to the different petrol station and the same result returned for your jerry can then it is your jerry issue and I am certain that is the can.

    • +4

      should hole 20L.

      a hole doesn't help.

  • I know upto 3% shortfall is allowable accuracy per the standard measurement, so 5% shortfall is just within the tolerable limit.

    i know many fuel station short change upto 12% and i have face it. This is because now days modern car give fuel consumption from your last fill till now and if you top up your tank everytime you fill then you will know how much you get shortchanged.

    I had encountered this issues with discounted American branded fuel station at casula NSW and very particular browser charged me more then 15% of what my fuel consumption information given by my car. I finally wrote to them and submit proof and also to department of fair trading. No one accepted the fault but i have noticed that they have got thier machine recaliberated after 2 weeks.

    So it's always advisable to write to thier HO with proof atleast they will get thier browser caliberated.

    Imagine if they dispense more then 100K ltrs a day they make easy money of more then $ 5K every day by snipping off fuel from each delivery they make without you even noticing it.

    If we all Ozbargainer starts this procedure to write an email when you are short delivered automatically fuel browser HO will start monitoring and will remain alert for this misbehaviour.

    • Agree with you that some stations short change. I usually run my tank down to quite low before filling and check my odometer as well as my fuel consumption in L/100 from the trip computer before calculating how much should go in. There is a station near me that is accurate to about 1-2 % every single time, yet doing the same technique with some other stations elsewhere, some can vary as much as 7-10% to the station owner leading to having to pay for an extra 3-5 litres of 98! I also verify by listening to the tank vent noise of the accuracy as when the tank just about fills, the vent noise will be different so that you get consistency as to when the tank is full.

      I have thought about reporting to NMI whenever I come across suspicious pumps but never bothered, just sticking to the servo that I know is accurate.

      Learnt something about how to look at the pump to see when it was last calibrated so will be on the look out.

  • Its just possible that your jerry can volume is the thing that is not accurate. The pump is most likely checked regularly, how about your can?

  • You can report this

  • Why don’t you get a 1000ml (1 litre) measuring cylinder and fill it 30 times (or 10 or 20) and compare to pump volume. If there is a slight error it will be more noticeable at a higher volume.

    • The volume is not accurate unless you dispense ~5L (most say min 2L sale on them). I wouldn't expect it to be across a 1L pump starting and stopping. So, OP would have to dispense into jerry can, then measure out carefully without spilling any

  • +14

    Hi all, first post as I’ve been lurking for a while.
    I’m NMI certified to calibrate fuel bowsers/ dispensers and do so on a regular basis. The allowable limits are +/- 0.3% but must be as close as possible to zero. Petrol and low flow diesel dispensers are usually calibrated using a 15 litre NMI certified measure and high flow diesel dispensers are usually calibrated using a 200 litre NMI certified measure. The measures are verified annually or bi-annually depending on how they are stored (risk of damage etc).

    • so what do they do with 200L of diesel once they've measured it?

      • +2

        pour it back into the tank. Some truck stops you could be doing 16+ high flows - you wouldn't keep your job long if you tried to take away 3,200L of fuel in a tanker!

        PS - welcome targaboy to the OzB world of commenting :)

    • +9

      Your factual and professional advice is not welcome here on OzB.

      This forum is specifically for armchair experts and conspiracy theorists pretending to know everything.

    • Thanks for your input. Are the checks done at random without the awareness of the station owners as I have noticed some quite abnormal pump accuracies over the years. What about software tampering possibility in these pumps even though the physical calibrations are quite accurate?

  • +1

    Your jerry can's measurement is incorrect.

  • Evaporation?

    • -1

      Nah, he had a sly sip on the way home and he's trying to shift the blame.

  • -1

    The weight of petrol is less than the weight of water so weighing minus the container weight won't work if that was used to measure

    But lets say you had 2 see through 1L container with correct markings and you filled one with water and one with petrol and the petrol only had like a little less that would suck but still acceptable

    Also not sure if you notice but when you start filling the fuel cans the first half second is usually air too

    • The weight of petrol is less than the weight of water so weighing minus the container weight won't work if that was used to measure

      So if something has a different weight to water it can't be weighed? Fuel just has a different density. Where water is 1kg:1L fuel is more like 0.75kg:1L.

      • of course it can but OP didn't specify how they measured

  • +1

    You are not only the one being ripped off. See below article.


  • +1

    If you look on the pump you will see the last time it was calibrated by your state authority.

    You can always complain to them who will send out an inspector and test it again.

  • +5

    Who can drink 30 litres of fuel and not get sick?

    • +1

      Chanting: Jerry! Jerry! Jerry!

    • +1

      He only drank 29 litres apparently

  • +2

    A jerry can is not a measurement device. The designed purpose is to carry fuel, not measure volume.

    The volume labelled on the container is just to give you some idea of approximately how much it holds. 5L, 10L, 20L etc

    They do not make any promise of accuracy or even attempt to calibrate these containers.

  • +1

    Next time you look at your petrol pump at the bowser , you will notice a small hole separate to the main hole where your fuel comes out.

    /puts on tinfoil hat

    besides collecting fuel vapors , the paranoid in me reckons it also takes a little bit of fuel back here and there from everyone without people noticing and OP noticed.

    /takes hat off

    …………….ill see myself out

    • +1

      Nah, you are actually right. It takes back vapours, but petrol evaporates pretty quick, so there is the "little bit" you mentioned.

      I'd say it is negligible unless it is really hot inside your tank/ put the jerrycan on the hot asphalt.

    • -2

      Lol - not quite, that little hole is what shuts off the nozzle when fuel enters it ie. your tank/ container is full.

      • +2

        Lol - not quite, that little hole is what shuts off the nozzle when fuel enters it ie. your tank/ container is full.

        Refer to this page 4

        The second process involves the capture of vapours through the pump nozzle via the
        modification of fuel dispensing infrastructure to create a vacuum that draws the fuel vapour
        back down into the underground storage tanks at the service station (these vapours are
        subsequently transferred to the fuel terminal/depot using VR1 processes)

        • I have not come across one yet in either Qld, NSW or Vic.

  • Standard jerry can is not a good way to measure the fuel. There are specialised calibration equipment that is used.
    Moreover, all fuel stations get audited random for fuel measurement by National Measurement Institute and if found not in compliance the company face hefty fines.

  • If the jerry can is plastic, they expand over time, if using the markings on the side of the jerry can it will indicate lower amount of liquid due to the plastic being larger.

    • +1

      This. All of mine have expanded in the middle and thus hold more. Bit like me in that regard

    • +2

      Yes, they swell up big time, especially in a hot shed. A common trick with the long range tanks on adventure bikes is to fill them with boiling water, and you'll get an extra 4 litres or so. This is not even necessary with a non vented jerry can.

  • Wonder if anyone ever checks the end price being volume times cost.

    Many years ago got ripped off with with a pump showing end cost was 10% higher than calculated price of volume times cost per litre.

    Often check by calculator after filling.

    • +1

      This is also part of the calibration verification being carried out. Verification of bowsers/ dispensers is not just calibration, also have to check it does not count air when air is introduced to simulate the storage tank running dry, price calculation at bowser and in store, check the preset amount operates and calculates correctly, the flow rate is within the range for that bowser, the nozzle shuts off correctly, the nozzle does not bleed out fuel and empty the hose for the next user etc etc.

  • Fuel excise is calculated at 15 degrees celcius equivalent volume. Do pumps measure volume at 15 degrees equivalent or ambient?

    • +1

      Fuel bowsers/ dispensers are at ambient as the amount pumped is too small for a noticeable difference. Bulk fuel meters are calibrated and then adjusted to 15 degrees C

  • +1

    OP: Tip the petrol out over the neighbours yard/driveway then fill the jerrycan with their water hose with 30L of water and see where it fills to.

  • Wow.

  • I don't know why I am wasting money buying volumetric glassware for my lab, I should be going to SCA and getting jerrycans.

  • Poor it out on your bathroom scales. Petrol is about 740g per litre so you should have 0.74x what ever your fuel docket said. But if you get less than 22.2kg you know you were ripped off.

    Pro tip: Measure your weight first! If you can't manage to get all 30 litres on the scale without it spliing off you can lick it off the floor, remeasure yourself then subtract your original weight to get the weight of the fluid!!!!

  • have you tried using jellycan? they are more accurate

  • Report it. Inspector will come out.

  • Weigh your empty jerry can at home, then fill it up. Weigh it again, and you'll know if the pump is accurate

  • +1

    My Jerry can bulged on the sides a little bit. This can cause it to hold more volume than intended. Also as I witnessed in few petrol pumps, they regularly test quantity and quality at each of their pump. Hope this is a standard and required by regulation. so this is likely caused by Jerry can.

  • I agree with t h e poster. I also measured 6 × 2litre buckets and the pump said it had dispensed 13 litres, meaning 1 litre more than I ACTUALLY re c ieved. Unfortunately before I could make a complaint, the police had arrived. When I get out of Guantanamo Bay I intend to follow up on this. Furthermore, another ozbargainer has been short changed on electricity so I have a voltimetre and will be at pine gap to check up on this scandal.

  • Contact the ACCC

    • That is all.

    'scuse me

  • Where's MythBusters when you need them

  • I use Schott reagent bottles to buy small amount of fuels for my garden tools and found the pumps pretty accurate. Also although it says min delivery 2L you can buy any amout you like. I think that 2L might have something to do with their calibration to achieve a minimum % accuracy.

  • You're telling me OP…. This is what happened to me just last week at Caltex https://files.ozbargain.com.au/upload/84209/87849/img_202103...

  • So based on this article there is 95% that your browser is dispensing correctly fuel.

    So unless the OP's fuel station falls in the 5% that are inaccurate, looks like a new jerry can is needed :-)

  • You need to calibrate your Jerry can first:)

  • It's caused by global warming.

  • You are accusing the service station without first checking carefully the volume of the Jerry can against a standard measure?
    Why are you not accusing the Jerry can manufacturer?

  • If you’re a little short next time, just top it up with some water, and give it a good shake.