Petrol Station Fuel Pump accuracy

**PNR888** · 21-10-2009 11:05 PM

Hi all,

It was to my amusement to find out that I could actually pump in 67L of petrol (1 click only) in to my 65L CU2 fuel tank while the trip computer display 20 km to empty prior fill-up. This happened this evening at my local woolworth/caltex servo Voltex Ron95 petrol.
I would normally get 800-900 km per tank.

A month ago I pumped in 64.2L in while the computer trip indicate 8km left, according to the 65L capacity theory, I would only have 0.8L of juice left. (this was at another woolworth/caltex servo)

but after pumping 67Litre in tonight, that made me wonder the accuracy of those pump. and "Are we really get the amount of petrol that we are paying for?"

Or does CU2's fuel tank have this "secret chamber" that holds more fuel than its official 65L capacity?

In both occasion, the weather was not hot at all, quite cool actually. so the vaporisation should be very minimal.

Your experience and thoughts are appreciated.

**curtis265** · 21-10-2009 11:07 PM

I don' tthink so.......

**Rudy** · 22-10-2009 01:00 AM

That happened to me at a 7 11 once, i filled 76L in a 70 tank. Crooks. Im concerned you said caltex as i go there now. Used to go shell , which has 'independently volume tested' on the tanks and always gave me the best mpg, but now im on 95RON and they dont have that at my shell, cant go there anymore. If your shell has 95 i would go there.

**hotdc2** · 22-10-2009 01:20 AM

I've always wondered this too. Many times i've noticed the $$ going up on the machine before I can hear the juice being pumped into my car. Dodgey as. Someone call A Current Affair lol

**buddah51au** · 22-10-2009 05:59 AM

If the fuel tank is 65 Litre capacity you could add a few liters for the filler neck if you fill it to the top. The most I have used to fill my CU2 was just under 63L, with trip computer reading 83 km till empty. I suspect the true capacity including filler neck is closer to 70 liters.

**tony1234** · 22-10-2009 06:06 AM

Problem is we'll never really know.Oil companies are shady as.

**chrome** · 22-10-2009 06:14 AM

I have a Scangauge II (fuel consumption meter) running off the OBD2 port of my Accord. The fuel usage is calculated from the ECU injector pulsing, which makes it highly accurate and is widely used by hypermiling groups.

One feature it has, is when you go to a station and fill up, it tells you the expected volume of fuel to top the tank up to full, based on what it has calculated. After filling till the nozzle clicks, I then set the ACTUAL volume into the SGII and adjust the % error. So after a few tanks, the trend normalises, and the expected % error of my car is around 1.5-2% (very acceptable).

I once went to a Shell fuel station that made that error jump to >10%! It meant the pump indicated a lot more fuel needed for topping up to full as compared to what the SGII expected. I thought it was a glitch, and ignored it. A few weeks later, I came back to this same station, and the error jumped again to >10%. The conclusion I drew from that experience was that the pump at the Shell station, was not calibrated right.

I later found out from a colleague that the same station had gotten into trouble in past times for dodgy pump calibration. It is a hit and miss affair, so I never assume all pumps are correctly calibrated.

**nickxau** · 22-10-2009 06:40 AM

Would it be legal/allowed to byo measuring container and just measure the pump output yourself?

**Mr_will** · 22-10-2009 07:28 AM

Originally Posted by nickxau

Would it be legal/allowed to byo measuring container and just measure the pump output yourself?

as long as the container meets australian standards and is <20L you can fill it at a service station.

i dont have any experience with shell, but I use to work for another brand of service station, and I know we regularly had the pumps calibrated.

I think it's unlikely that servos are doing anything shady, for the simple reason that the fines would be astronomical, and the service stations actually only make a few cents per litre on your fuel - their profit comes from the goods you buy in store.

**89superstage** · 22-10-2009 10:15 AM

Hi all,
My first post on OzHonda.
I have'nt had my CU2 for long but, I've had this experience as well.
Fuel filler clicked,this morning, after dispensing 64.4L, but the Trip said, I had 40km till empty. @10.9L/100k....
I'll try the Shell across the street next time and see how much go's in.

Did notice though that the tank had filled almost all the way up to the brim, without me trying to squeeze more in.

**chrome** · 22-10-2009 11:12 AM

Originally Posted by Mr_will

as long as the container meets australian standards and is <20L you can fill it at a service station.

i dont have any experience with shell, but I use to work for another brand of service station, and I know we regularly had the pumps calibrated.

I think it's unlikely that servos are doing anything shady, for the simple reason that the fines would be astronomical, and the service stations actually only make a few cents per litre on your fuel - their profit comes from the goods you buy in store.

If their pumps are miscalibrated to say 5% inaccuracy, it means they actually charge consumers for 105 liters for every real 100 liters sold. That's a profit of ($1.20 x 5) just from inaccurate calibration, plus the few cents per liter from the legitimate 100 liters. Depending on the volume of petrol sold every day, that could account for a fair bit of $$ profit.

**buddah51au** · 22-10-2009 11:36 AM

Originally Posted by chrome

If their pumps are miscalibrated to say 5% inaccuracy, it means they actually charge consumers for 105 liters for every real 100 liters sold. That's a profit of ($1.20 x 5) just from inaccurate calibration, plus the few cents per liter from the legitimate 100 liters. Depending on the volume of petrol sold every day, that could account for a fair bit of $$ profit.

My understanding is that when pumps are calibrated the allowable tolerance is + or - 2%. Someone within the industry would know if in fact that is still the case these days.