Fuel station pump calibration.
Submitted: Sunday, Nov 04, 2012 at 13:07
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Polaris
This has been a concern of
mine for some years.
I've had many instances where the amount of fuel displayed on the pump meter is way OVER what I got!
I do realise that if I'm topping up a tank and only going on the vehicle fuel gauge (which is NOT linear) then I'm lucky to estimate to the closest 10L the amount that is needed to fill the tank. I accept this.
However - when I'm filling an empty tank or container of known capacity, then I feel that the dispensing pump should give me correct measure.
A few examples ....
Filled a 20L 'Spectre" red jerrycan, which has a number of 'guide' calibrations moulded into the opaque plastic. I stopped at the top '20L' line and was amazed when I turned to see the fuel bowser displaying 27 Litres!!! The pump was definitely zeroed prior to starting by the console operator. When I questioned the accuracy and wanted to know when the pump was last checked for calibration - I simply got a blank stare from the junior console operator. I had to pay for 27 litres!
The 'Sub' tank in our Nissan Patrol is shown as 30L in the vehicle specs. Most times it 'clicks' of at 30.2 to 30.6 litres to fill the tank. There have been many instances where the bowser indicates figures up to 36 Litres!
Our dual fuel Ford F150 had 2 gas tanks. When empty, the normal amount to fill them was 78 to 79 litres before the nozzle auto clicked off. To my dismay one day it was showing 100 litres and still pumping!!
I can accept that there may be times where the pumps get out of calibrtion due to error or adjustment of some sort - but how come these innacuracies are always in the fuel suppliers favour? Simple logic and averages say that there should be some that short supply and some that over supply.
All the questionable suppliers have been Woolworths or Coles sites !! Have never had the occurence happen at an independant.
I'm in Queensland and tried to contact the Department of Weights and Measures - only to find it seems that they no longer exist and 'self certification' is now the go!
Something fishy here - the major supermarkets are supplying 4c fuel discount on purchaes >$30 which on $1.50 fuel equates to a 2.66% discount - then they jack up the price by fiddling the calibration by up to (in my case) 7 litres extra in a 20 litre container =35% !!!
ANYONE ELSE WITH SIMILAR EXPERIENCE ???
Reply By: Hairy (NT) - Sunday, Nov 04, 2012 at 13:15
Sunday, Nov 04, 2012 at 13:15
Gday,
Im not saying I disagree, but thats a hell of an acusation to make on a bublic
forum isnt it? Be carefull.
Cheers
AnswerID:
497895
Follow Up By: Polaris - Sunday, Nov 04, 2012 at 13:25
Sunday, Nov 04, 2012 at 13:25
Actually not really an accusation - simply shared experiences that have happened to me.
It is an issue that affects all of us who drive and buy fuel.
In years gone by (in Qld at least) fuel station pump accuracy was regularly checked by the Department of Weights and Measures. Often systematicly each lane was blocked off by a vehicle and trailer carrying the calibration equipment. The same used to happen in supermarkets and grocery stores where the weighing scales for fruit, vegies, meat fish etc were all checked.
Doesn't seem to happen any more ...
FollowupID:
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Follow Up By: Hairy (NT) - Sunday, Nov 04, 2012 at 13:45
Sunday, Nov 04, 2012 at 13:45
Yeah your right.......I havent seen them measureing the fuel for years.
Only yesterday I filled up my daughters new/secondhand Rodeo ute with Diesel. I seemed to take bloody ages to fill and cost $50 something bucks. What was odd was the fuel gauge was on 3/4....It was the first time I filled it and dont know the tank size , but it makes you wonder hey?
Cheers
FollowupID:
773800
Follow Up By: MEMBER - Darian, SA - Sunday, Nov 04, 2012 at 13:50
Sunday, Nov 04, 2012 at 13:50
Actually - yes - really - that is an accusation ("then they jack up the price by fiddling the calibration by up to (in my case) 7 litres extra in a 20 litre container =35% !!!"). Maybe you are correct though - what does the proprietor of the fuel outlet have to say about it ?
FollowupID:
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Follow Up By: Shaker - Sunday, Nov 04, 2012 at 19:59
Sunday, Nov 04, 2012 at 19:59
He didn't accuse anybody, merely named a retail chain, as I won't name anybody specific, other than to say the worst case that I have experienced was at
Wiluna.
FollowupID:
773840
Reply By: Axle - Sunday, Nov 04, 2012 at 13:53
Sunday, Nov 04, 2012 at 13:53
G/Day Mate, I fill 20L containers up everyday from servos, and at times have frowned when 24Lhas filled one. All in all though, in NSW i think pump accuracy is not to bad.
I would fill a container again at the same servo, then try somewhere else with an other one the same, if there is a big you descrepency then have a case to fight.
Cheers Axle.
AnswerID:
497896
Follow Up By: ozjohn0 - Sunday, Nov 04, 2012 at 16:32
Sunday, Nov 04, 2012 at 16:32
20 litre Jerry Cans are designed to take 20Lt with a safe air space for expension at the top.
Most will take 25 plus litres, but filling to the top is a dangerous practice.
Ozjohn.
FollowupID:
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Follow Up By: Axle - Sunday, Nov 04, 2012 at 21:09
Sunday, Nov 04, 2012 at 21:09
I know that Oz john, But allowing for air space i.ve had a odd one take extra litres.
Cheers Axle.
FollowupID:
773847
Follow Up By: R Send - Monday, Nov 05, 2012 at 08:11
Monday, Nov 05, 2012 at 08:11
OJ,
The OP said he filled the container to the 20l mark, not to the top! You'd think that the "calibration" on the container might be reasonably accurate, wouldn't you?
Phil
FollowupID:
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Reply By: Member - eighty matey - Sunday, Nov 04, 2012 at 14:22
Sunday, Nov 04, 2012 at 14:22
We have a friend that works for Fair Trading in NSW.
They have a vehicle made specifically for testing the accuracy of fuel pumps.
Part of his job is to randomly
check fuel pumps all over the State for accuracy. He says most pumps are accurate and if anything they dispense more fuel than the pump shows.
They also
check scales and packaging for accuracy in shops.
Steve
AnswerID:
497901
Follow Up By: Member - John and Val - Sunday, Nov 04, 2012 at 16:50
Sunday, Nov 04, 2012 at 16:50
We saw one working in WA recently -
Esperance I think.
Cheers,
Val.
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Follow Up By: Polaris - Sunday, Nov 04, 2012 at 17:20
Sunday, Nov 04, 2012 at 17:20
Queensland also once had this checking facility. No more it seems. Now it is law of the jungle with self certification.
We have already seen some of the catastrophic events in the electrical and building industries as a result of "self certification".
Can't blame 'Can -Do' alone for this though - government cut backs have been going on for decades.
Eg - Qld Health used to test for mercury content in fish - but not since 1998!
FollowupID:
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Reply By: Michaeljp - Sunday, Nov 04, 2012 at 14:27
Sunday, Nov 04, 2012 at 14:27
Contact the "department of fair trading" in your state.
AnswerID:
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Reply By: Racey - Sunday, Nov 04, 2012 at 16:47
Sunday, Nov 04, 2012 at 16:47
Blow molded 20 liter containers are not what you would call a calibrated containers. Even when filled to the marked line. As previously mentioned, they are not designed to filled to the brim. Fill you container to the line and compare that with another station when filled to the same line. Alternatively dispense 20 liters from 2 different station and mark the difference on the container. If all else fails go to fair trading.
AnswerID:
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Reply By: Member - Chris & Debi (QLD) - Sunday, Nov 04, 2012 at 18:17
Sunday, Nov 04, 2012 at 18:17
I have recently seen pumps being checked on the Sunshine Coast and by doing some research on the net find that stations still get checked regularly.
What used to be a State responsibility has been taken over by the Federal Gov as per then following taken from their web site
Since 1 July 2010, the National Measurement Institute (NMI) (a federal government agency) took responsibility for trade measurement in Australia from the States and Territories.
The NMI is responsible for developing and maintaining Australia's standards of measurements. The NMI also employs inspectors to monitor compliance with the trade measurement standards.
Chris
AnswerID:
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Reply By: Road Warrior - Sunday, Nov 04, 2012 at 19:24
Sunday, Nov 04, 2012 at 19:24
In WA they used to do annual checks on fuel pumps and dispensers. This was the Department of Fair Trading but I don't know what the inspection regime is now.
How it was explained to me by a Gilbarco technician once was that if a pump or dispenser (yes there is a difference) was out of calibration they way they were set up it was more likely they would over-deliver than under deliver. They said it would be quite unusual if they found a pump or dispenser that was under delivering and over charging, and it would warrant a bit closer scrutiny to see if the unit had been tampered with.
AnswerID:
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Follow Up By: R Send - Monday, Nov 05, 2012 at 09:14
Monday, Nov 05, 2012 at 09:14
And the difference is....?
Phil
FollowupID:
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Follow Up By: Nomadic Navara - Monday, Nov 05, 2012 at 09:44
Monday, Nov 05, 2012 at 09:44
There are two main parts to a bowser, the pump which lifts the fuel from the tank and the dispenser which meters and delivers livers the fuel to your vehicle. It's not the pump that is calibrated, it's the dispenser that is calibrated.
FollowupID:
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Follow Up By: R Send - Monday, Nov 05, 2012 at 17:57
Monday, Nov 05, 2012 at 17:57
Peter,
Thanks for that! - all is clear now.
Phil
FollowupID:
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Reply By: Dust-Devil - Monday, Nov 05, 2012 at 02:25
Monday, Nov 05, 2012 at 02:25
How long is it going to take you dudes to realise that you have 'magic tanks/containers' that were deliiberately manufactured to hold more than stated, so as to confobulate the servo operators.
Think yourselves lucky, as not all of us have these wonderful items.
AnswerID:
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Reply By: Ol' Bunky - Monday, Nov 05, 2012 at 09:40
Monday, Nov 05, 2012 at 09:40
At a roadhouse I pulled into once, I managed to fit 235 litres into a 205 litre drum. When I queried the bloke he said "It's a hot day, it'll do that" Would have thought a cold day would do that but anyway.............
AnswerID:
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Follow Up By: Nomadic Navara - Monday, Nov 05, 2012 at 09:45
Monday, Nov 05, 2012 at 09:45
A drum should not be filled, you should leave a considerable air space to allow expansion.
FollowupID:
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Follow Up By: Bazooka - Monday, Nov 05, 2012 at 16:16
Monday, Nov 05, 2012 at 16:16
I think you mat have hit on one of the reasons Bunky. I haven't got a clue as to the temperature variations in underground tanks (obviously depends on the area) but I've seen figures like 1% difference in volume for every 5 degrees increase in temp at around the 20 degree mark. I presume this means that if a pump has been calibrated in winter when the tank/fuel temp could be say 10 degrees then you could get 1% less for your money in summer when the tank temperature might be 15 degrees. That doesn't account for anything like the numbers being suggested above.
Moral: if you are worried about every last penny then fill up early in the morning after the tank/fuel has had time to cool over night and don't fill up from above ground tanks if possible. Possibly.
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Follow Up By: Nomadic Navara - Monday, Nov 05, 2012 at 17:52
Monday, Nov 05, 2012 at 17:52
Quote "Moral: if you are worried about every last penny then fill up early in the morning after the tank/fuel has had time to cool over night and don't fill up from above ground tanks if possible. Possibly."
I don't think so -
Read this link
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Follow Up By: Bazooka - Tuesday, Nov 06, 2012 at 00:08
Tuesday, Nov 06, 2012 at 00:08
Which part don't you agree with Peter? The cooler the fuel is the more dense it is, hence you get "more for your money" comparatively speaking. There are lots of variables (which is why I said possibly) but more likely than not the tank temp should be a little lower after overnight cooling.
FollowupID:
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Follow Up By: Nomadic Navara - Tuesday, Nov 06, 2012 at 00:40
Tuesday, Nov 06, 2012 at 00:40
Looks like you did not read the link. It clearly states that there is very little change in temperature in the underground tank over the day. In other words you will get the same density of fuel no matter when you fuel up.
FollowupID:
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Follow Up By: Bazooka - Wednesday, Nov 07, 2012 at 10:09
Wednesday, Nov 07, 2012 at 10:09
I must have misread it then Peter because I can't see anywhere that he says conclusively that tank temperature is definitely not a factor. Nor does he provide any evidence regarding tank temperature variations. In his last two paragraphs under that particular fuel saving topic he seems to me to suggest that he really isn't sure:
"Others maintain that regardless of the temperature at which gasoline is delivered, due to the insulative properties of underground storage tanks one can't be sure that gasoline will always be at its coolest early in the morning.
In any case, the bottom line is whether it's really worthwhile for consumers (in the absence of ATC) to take matters into their own hands and attempt to save money by buying gasoline only at a particular time of day. Even if the temperature/volume issue were a real and significant one, one has to consider the amount of savings to be gleaned from such a scheme. Assuming that a motorist typically bought 15 gallons of gasoline per week at $4.00 per gallon, and assuming that by carefully choosing to fill up at a particular time of day said consumer could realize a 1% savings, we calculate the total savings to be gleaned over the course of a year at about $31. Would that reward really be worth the potential inconvenience of adhering to a rigid fill-up schedule week after week?"
I think his conclusion might be correct (in most cases) simply because ground temperature variations are nowhere near ambient temperature variations - but he offers no facts or figures regarding tank/fuel temperature variations and gives no parameters to his conclusion. My guess is he's talking about 'average' metropolitan "gas" stations (presumably all built of similar materials, in similar ground) in areas where day/night temperature fluctuations are 'average', say 20 degrees.
The most commonly quoted figure for density variation seems to be ~0.5% per 5 degrees C. That MIGHT be significant when comparing winter fuel and summer fuel but my gut feeling is that, in general, it's insignificant when talking about the best time to fill up. That's why I added "Possibly" at the end of my initial follow up. 'Fuel misers' might think otherwise.
FollowupID:
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Reply By: Member - Bruce C (NSW) - Monday, Nov 05, 2012 at 14:33
Monday, Nov 05, 2012 at 14:33
Hi Polaris,
It is easy to check. All you need do is go to Vinnies and get a measuring jug, near enough for your purposes, and if in doubt measure out the contents of your plastic jerry can.
If a 20 litre fill is out by any more than 5 persent or 1 litre I would be complining to Dept of Fair Trading in your state. If a discrepancy is found also check the fuel temp and record that also as fuel is picked up from the refinery showing X amount of litres at Y temperature I believe. The two are directly related as temperature will change volume but by how much I have no idea. But remember that fuel coming from under ground tanks will have a fairly constant temp so fluctuations should be minimal.
Remember if there is a problem you have a right and a responsibility to report it if you have found a discrepancy.
Fair Trade in NSW, according to my brother who works in a servo, pull into the garage unanounced and proceed to test the pumps any time they feel like it but usually on a regular timed basis, as he said, without warning.
Cheers, Bruce.
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Follow Up By: Member - John and Val - Monday, Nov 05, 2012 at 15:57
Monday, Nov 05, 2012 at 15:57
Bruce,
How accurate would you expect a "Vinnies jug" to be? Bit or room for error in that approach?
You could be a bit more scientific and weigh the full fuel drum (after having weighed it empty first).
If the drum was holding 20l of
water it should weigh 20kg plus the weight of the drum.
Petrol has a "weight" of about 740gm/litre so 20 litres of fuel should weigh approx 14.8kg
Diesel has an approx "weight" of 840gm/litre so 20 litres should weigh 16.8kg.
Cheers,
Val.
| J and V
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Follow Up By: Member - Bruce C (NSW) - Monday, Nov 05, 2012 at 20:30
Monday, Nov 05, 2012 at 20:30
Hi Val,
I would imagine that the vinnies jug would be accurate enough over the said 20 litres than the 7 litres overcharge difference the OP mentioned. A 2 litre coke bottle would do as
well as the law is specific in that if you say it has 2 litres of content then it had better have close to that if not more, so that would be a safe bet.
It does not have to be exactly accurate but sufficient to know if you are being ripped off or you are getting close enough to give the supplier the benefit of the doubt.
What would you reckon Val, could I get close enough using a jug from the kitchen to be close enough to the correct amount than the 20 litres in the drum for the 27 litres shown on the bowser as mentioned. I think I might get e reasonable ball
park idea. You could forgive a litre but 7 litres seems way over the top and certainly would warrant investigation IMHO. After all that is 30 percent potential overcharge if the OP is correct.
I acknowledge your point as regards accuracy but I would think it may be close enough to put ones mind at rest.
Cheers, Bruce.
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Follow Up By: Member - John and Val - Monday, Nov 05, 2012 at 20:48
Monday, Nov 05, 2012 at 20:48
Hi Bruce,
You may
well be right in that it could be "close enough". However given that the jug may not be accurately marked in the first place, and that you would have to fill it a few times thus introducing another source of error it would only be "close".
I'm just suggesting an alternative method that might be less fiddly and fairly accurate, (providing your bathroom scales are accurate!) so you had a firmer leg to stand on if you wanted to take the matter further.
Cheers,
Val.
| J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
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Follow Up By: Joe G2 - Tuesday, Nov 06, 2012 at 10:36
Tuesday, Nov 06, 2012 at 10:36
Then throw in another variable, fuel weight per litre varies with altitude.
Great thread everyone.
Joe.
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