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)?
Fuel Pump Is Not Accurate
justwii on 22/03/2021 - 20:41
Comments
- 1
- 2
Is it OK to name it here?
Nah illegal in every country except for Iran to name a business that wronged you.
Shh, you've said too much
That's like the best comment I've seen ever on the public forums on ozbargain.
Is it OK to name it here?
At your own risk, of course. The last guy who did it was tracked down and shot while he was sitting in the dunny.
As long as you are telling the truth, why wouldn't it be not ok?????
Not this again. Your Jerry can doesn't hold exactly 30 litres. You are meant to leave room for expansion. There is generally even a line on them they tell you to stop filling at.
this.
Good advice. I was actually using the line as my reference point, it was not even touching the line yet but fuel pump said 30L already. Is touching the line 30L exactly?
Depends on the weather
It was foggy.
^This. Fuel density varies greatly based on temperature, colder weather it's more dense and in hot weather less dense. Try doing the same thing on the same pump in winter, first thing in the morning and you'll be at or above the same line. In addition to that, if the jerry can was expanded prior to filling, then that will play a part as well. In cooler months my 20L cans will hold about that much.. if I accidentally let them shrink then it'll be even less. In summer I can squeeze 24L into the same jerry cans before it becomes tricky to pour next time.
@MrKnowItAll: There is no weather under the ground where the fuel is stored. Fuel temperature will remain fairly stable.
@cydia9k: No that's what I'm saying, the effects of the weather aren't there.
The underground temperature remains stable regardless of what is going on above.
@trapper: Well I'll admit I have no experience on which to base my assumptions, but I'm having a hard time believing that the underground density will remain the same on a 15° day vs 43°
@cydia9k: Ummm…. you only need to be about 3m meters underground for the air temperature to have zero effect on the ground temperature almost anywhere in the world. Just try heating your oven to 200 degrees, place a roast in the middle of the oven and fill the rest with dirt and time how long your roast takes. (HINT: don't do this as it'll probably stuff your oven, and not cook your roast).
Well I'll admit I have no experience on which to base my assumptions, but I'm having a hard time believing that the underground density will remain the same on a 15° day vs 43°
Earth has very high thermal mass. The temperature will not change and the density will not change.
@MrKnowItAll: So are you saying that the petrol flowing into your car from the pump is measured in mass rather than volume?
If the temperature in the Jerry can and the pump is not that different and the petrol is measured in volume, 30 litres from the pump should be 30 litres in the can.
The 30L in your can is 30L of water. 30L of petrol takes less room than 30L of water.
The 30L in your can is 30L of water. 30L of petrol takes less room than 30L of water
And , I assume following that same science, 1kg of water weighs less than 1kg of petrol?
@SBOB: No, because of the different density of the molecular structure (neutrons/electrons density) the same weight of petrol and water will have different volume.
@Chchnu: NOOOOOO. Just no. Water has a density of 1 kg /L, that is, 1 liter of water has a mass of exactly 1 kg. Oil has a lower density than water: about 0.91 kg / L. That is, 1 liter of water and 1 liter of oil have the same volume, but 1 liter of water is heavier than 1 liter of oil.
So 1L is 1L, volume is the same, but their mass is different.
The definition of a Litre - a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3). A cubic decimetre (or litre) occupies a volume of 10 cm × 10 cm × 10 cm (see figure) and is thus equal to one-thousandth of a cubic metre.
This is independent of what the Litre is made of.
@Smol Cat: That can't be right because if it was then 1kg of petrol will weigh the same as 910 grams of water.
@Chchnu: Let me put it this way. Is 1m^2 of gold sheeting the same area as 1m^2 of paper? Even though their weights and densities are vastly different?
It's this, but now imagine 1m^3 for the items. Same volume, different densities/mass.
No, because of the different density of the molecular structure (neutrons/electrons density) the same weight of petrol and water will have different volume.
what are they teaching kids in school these days :/
@trapper: None of them are making any allowance for evaporation either. It would have a massive effect!
Or who is to say jerry can is the source of truth?
Fair point. Guess the stuff there can say the same, I need some stronger proof next time.
You need a high quality standardised jerry can that comes with an undeniable level of proof of accuracy.
OR. Buy 30L of bottled water and pour it in and see how high the water gets compared to the line?
@buckster: @buckster I know you know this,
But how are any of us to know if the 30L of bottled water is measured/dispensed accurately@original15: The alternative is that 1L of pure water (e.g. demineralised) weighs 1kg at 4 degrees celcius.
You could put the jerry can on scales and tip in water under controlled thermal conditions till you hit 30kg and see where the level is.
@buckster: @buckster please how can you expect me to trust scales given current discussion on measurement
@original15: If you could get your hands on access, or have a good balaclava you could enter the National Measurement Institute and borrow one of their two copies of the IPK. (International prototype Kilogram).
Then you'd know if your scales were accurate?
@buckster: Not accurate enough these days OP will need a Kibble balance since in 2019 the kg was redefined.
@deme: Well, in 2021, even that has now been replaced. The new unit by which all volumes and weights are measured against seems to be the jerry cans from Supercheap Auto.
The "kg" designation will henceforth be replaced with the "jc" symbol. Litres (l) will also be replaced with "jc".
@pegaxs: Yeah, I'll get a roast chicken cut into quarters and a 0.04166666666666666666666666666666666666666666 JC Pepsi Max.
enter the National Measurement Institute and borrow one of their two copies of the IPK. (International prototype Kilogram).
Then you'd know if your scales were accurate?
Hate to break it to you, but even the IPK isn't trustworth anymore
you could enter the National Measurement Institute and borrow one of their two copies of the IPK
Or you could just ask them nicely when was the last time they audited or calibrated the servo's fuel pump…
@original15: I weigh breadmix into 500mg portions with an electronic scale. Did it outside on rough concrete surface. Some 500gm portions were 750mg!!! Huge error by not using a smooth level hard surface. How accurate is the scale anyways, and how do we know all conditions are met…. no point worrying about 1-10% :)
Some 500gm portions were 750mg
Seems like a difference easily identified without scales ;)
how are any of us to know if the 30L of bottled water is measured/dispensed accurately
Lol, I was expecting this conversation to become abstract to the point of… are any of us even actually alive, or is it all just a simulation? X-Files theme plays
@original15: Easy. You use a fuel pump to dispense 30L of fuel into the water bottles. You can tell when you have the right amount by looking at the display.
@buckster: Hoping you don’t get 30 inaccurately filled water bottles though lol might compound the issue if each bottle had say 1025ml
@buckster: You can't trust bottled water either - as they might overfill (seeing as water costs almost nothing). You could use water and a well calibrated set of scales.
@MrFunSocks: That's not the point. It's that you are not getting what you are paying for.
And maybe it's a dollar person or thereabouts, but scale that up to the number of customers they get per day, and it becomes a lot of money everyday.
Also interesting is how the errors are always less, never more.
The servo pumps are checked and calibrated. The Jerry can is not calibrated at all. The servo pump will be very accurate, the Jerry can will not be accurate.
This, my jerry can is a 20lt one, probs has room for 22 litres
Pretty sure the fuel pump charges you at the top of the fuel pump, so the start of the tube. If you don't shake out what's in the tube then you don't get your full money's worth.
Lol. Now I’ve heard everything… Let me guess, also more than two shakes is playing with it?
And for the players at home, this is not how fuel guns work. I see so many people at fuel stations pressing the stop on the pump and pulling the trigger thinking they are getting that last bit out of the hose. Once the pump stops and there is no pressure in the hose, the fuel gun doesn’t open.
But please, if you are one of these people that does that at fuel stations thinking you are getting an extra litre or two out of the hose, please don’t stop, I love a good laugh.
A good video from Husky helps explain how they work.
more than 2 is playing, but it take 5 to get it up.
I sing that song every time I finish pumping my car up.
Some people do it to stop dripping. Perspective aye.
shake out what's in the tube
Not necessarily limited to fuel pumps
Pretty sure the fuel pump charges you at the top of the fuel pump, so the start of the tube.
No it doesn't.
But it doesn't matter where they are because the entire hose is full of petrol
So the person before you 'paid' for the petrol that's already in the hose, you leave fuel you have paid for in the hose for the next person when you leave. The net effect is zero.The location of the flow metre only makes a difference if the hose was drained and full of air because you would then need to prime the hose with fuel. Bowers are designed so that this never happens.
Bring a set of scales next time. A litre of petrol is roughly 750g. But this will change based on the altitude and temperature at your local. Your mileage and maring of error may vary!
Easy enough to weigh the empty container at home, fill the container and keep a record of amount dispensed, then weigh the container when back home, sample weigh a litre of fuel and verify.
What if some of it evaporates due to a poorly fitting lid?
What if Jesus returns between servo and home?
What's likely more accurate…
The 10 dollar mass produced plastic jerry can or the calibrated fuel pump worth $10s of thousands of dollars?Yep, most likely that jerry can…
honestly, probably the jerry can.
That's what I was gonna say. Probably cost 10 cents in materials to make, it isn't made to NASA-grade standards.
We could argue that something that had thousands compared to dollars is better or not but if we use this analogy my google gps says im doing 56 in a 60 zone but the cops said i was doing 63 which is more accurate google that spent millions or cops that spend roughly $10000 on a Radar/LiDar?
To take that further, you're comparing your phone cost vs the Radar….or if you really get pedantic, the cost of the GPS module :)
Nah, gotta count the cost of the GPS satellites as well, which if memory serves requires at least 4 satellites in space for your phone's GPS to work.
And the pump has to be regularly serviced and calibrated.
I don't know about the OP, but by plastic jerry can can expand and contract at least 10% just based on the pressure built up inside it and the changes in temperature. Even the large metal jerry cans have pressed metal walls which can pop in and out to some degree.
Also the jerry can is not even designed to measure fuel volume.
The 10 dollar mass produced plastic jerry can or the calibrated fuel pump worth $10s of thousands of dollars?
That's like saying large HR and payroll systems worth and costing hundreds pf thousands of dollars are trustworthy, yet people get screwed over all the time. That jerry can does not have any motivation for cough profit making.
(Yep, I'm damn cynical, but no I don't think I'm actually getting shafted at the servo)
Petrol bowser inaccuracies on the rise
Try another servo and you might get to your line after only 29 litres!
Here we go! It's Jerrycan-gate…
0.3 - 0.9% out? That's pretty good. The variation in fuel consumption in a car caused by different driver moods on any given day would cause greater variation than that.
Or window down, air conditioner usage, headlight eye lashes, etc.
Hell, temperature change of the liquid will effect the volume more that much. Apparently it's about 0.1%/deg celsius. https://autoexpert.com.au/posts/petrol-vs-temperature
The temperature of such a large volume of fuel stored in underground tanks would be very stable though.
@trapper: The underground tanks will have very stable environmental conditions, the cheap jerrycan less so.
@Krankite: While being filled though, the temp of even the cheapest jerry can will match the temp of the fuel from the underground tanks.
It will gradually warm up over the next few hours to match the conditions where the jerry can is stored.
@trapper: Is a pump calibrated to dispense a certain volume of fuel (or is it measuring weight at a certain temp and pressure, and attempting to deliver that weight of fuel, and thus an approximated volume?
If so, it the density can get affected by the amount of condensation, (dissolved water) the pump is working with… tolulene, or whatever else they mix in with it to make mo money and fool the checkers from the industry bowser accuracy consortium.
1 liter of petrol weighs 0.737 kilogram
weight an empty jerry can before you pump fuel into it, then weight after. if you cap it immediately, evaporation will be negligible.
get all the measurements on your next trip and create another post.
How accurate are OPs scales?
weight it across a few scales. choose the one that will reinforce his point
+/-5%
- 1
- 2
which fuel provider was it? BP ? Caltex?Private metro?