Filling the gas tank - which was wrong?

[Gary_T]

Gas pumps are checked and certified yearly by a government agency (here in Missouri, certainly, and likely in all states). The pump apparatus gives an accurate and rather precise readout. Vehicle gas tank volume figures are somewhat nominal - we’re not talking about filling a precisely calibrated piece of laboratory equipment. So in answer to the OP, the tank volume spec is “wrong.”

[Pushkin]

@Santo Rugger

*My car has a lot of funky things like that. For example, to completely disable the traction control, you have to turn the key to the *start *position for five seconds while the vehicle is running! To disable the seat belt chimer, you have to put the key in the accessory position, insert and remove the belt three times, move the key to the on position, insert and remove three times, then back to the *accessory *position and insert and remove three times. Don’t even get me started on how to get the vehicle computer codes to pop up!

But how do you enter invincibility or all ammo modes?

[vetbridge]

@Santo Rugger

To disable the seat belt chimer, you have to put the key in the accessory position, insert and remove the belt three times, move the key to the on position, insert and remove three times, then back to the *accessory *position and insert and remove three times.

Wow. I’d prefer to just cut the damn wire!

[Otto]

@Santo Rugger

*My car has a lot of funky things like that. For example, to completely disable the traction control, you have to turn the key to the *start *position for five seconds while the vehicle is running! To disable the seat belt chimer, you have to put the key in the accessory position, insert and remove the belt three times, move the key to the on position, insert and remove three times, then back to the *accessory *position and insert and remove three times. Don’t even get me started on how to get the vehicle computer codes to pop up!

How do you even discover these things?

[John_DiFool]

@ZipperJJ

The “almost out of gas” light came on on my 2004 Escape last week. I did a few short trips around town before I got around to filling up.

My tank is reported to be 16 gallons. According to the gas pump, I put in exactly 16 gallons on the nose that day.

So which is off? Is my tank actually over 16 gallons or is the gas pump fudging numbers? Or had I literally used the absolute last drop of fuel in my tank the second I pulled up to the pump?

True story-I was driving to my mom’s house in Ohio a few years back, got off the interstate, and 10 miles into Amish territory I only then bothered to notice that the needle was on “E”. I stopped and asked some local (non-Amish) kids where the nearest gas station was, and they mumbled something about “several miles ahead”. So I kept driving, praying and hoping that I’d find the station before she conked out. Eventually a Sunoco station came into view-yeah! I filled her up until the safety valve shutoff was reached, and then noticed the gallons. 11. My tank’s capacity, according to the manual? 11. The only fuel left was that in the fuel line (or, once you count the filling tube leading to the tank, the capacity is a bit higher than 11).

[Dog80]

Damned coincidence! Today a guy in an Opel Astra came to my petrol station with the fuel light turned on. We filled his tank and it took 48.5 liters. He complained that the car’s manual says that the tank capacity is 46 liters. This happens every now and then.

I am confident that my pumps are dead accurate (they get routinely tested by both the government commerce agency and the company that provides me with petrol). The problem is that these customers sometimes behave really badly and complain loudly, threatening with lawsuits etc. and this ain’t good for my bussiness.

I am going to print that article from physorg.com and show it to anyone who complains. I also found the original NIST article here: http://ts.nist.gov/ts/htdocs/230/235/archive/B-014.pdf (PDF)

[Santo_Rugger]

@Otto

How do you even discover these things?

I treat my car kind of like video games… up up down down left right left right B A start.

I spend a bit of time at the Charger Forums.

[lobotomyboy63]

@Santo Rugger

Sublimatin is when a solid that is warming skips the liquid phase and goes straight into the gas phase. This occurs when the ambient pressure is much lower than the liquid’s vaporization pressure. Gasoline (and many petroleum products) have a vapor pressure much higher than one atmosphere. I doubt there is more than 1/100 of a gallon lost to vapors during filling up.

Thanks, Santo, for the clarification. Sublimation didn’t sound like the right word; that’s like how dry ice doesn’t liquefy, just goes directly to gas, or SRBs on a shuttle launch.

Isn’t there a term for what I’m thinking of? Sometimes here, after the air has been dry for weeks during the winter, it’ll rain. But the water quickly disappears from the pavement and other non-absorbent surfaces. I think the dry air just reabsorbs it but I don’t know if that qualifies as evaporation, which I associate with the application of heat.

What’s the deal with vapor recovery nozzles, if there’s not much loss to vapors? Safety, in case of a spark? The person filling up experiences a toxic cloud? Environmental concerns?

[Terminus_Est]

@lobotomyboy63

Thanks, Santo, for the clarification. Sublimation didn’t sound like the right word; that’s like how dry ice doesn’t liquefy, just goes directly to gas, or SRBs on a shuttle launch.

Isn’t there a term for what I’m thinking of? Sometimes here, after the air has been dry for weeks during the winter, it’ll rain. But the water quickly disappears from the pavement and other non-absorbent surfaces. I think the dry air just reabsorbs it but I don’t know if that qualifies as evaporation, which I associate with the application of heat.

Evaporation. Heat increases the evaporation rate, but is not necessary for it to occur.

[Santo_Rugger]

@Terminus Est

Evaporation. Heat increases the evaporation rate, but is not necessary for it to occur.

Evaporation is a special case of vaporization that happens below the critical temperature. If the vaporization happens above the crit temp, it is boiling.

[lobotomyboy63]

Plain ol’ evaporation, eh? Learn something new every day. Thanks.

[ZipperJJ]

Hey cool, Dog80, that’s great first-hand info from a real station owner!

I wouldn’t put it past this particular station to fudge the amounts a bit - it was a GetGo station who’s main gimmick is per-gallon gas discounts for people who use the bonus card at the grocery store chain that owns the stations. So they pretty much only exist to get people to shop more at the grocery store.

But, Dog80 says his pumps are accurate and they dispensed 2.5 liters more than the customer’s tank size…so I’ll believe that my station’s pump can dispense exactly as many gallons as my tank size, without assuming any funny business.

Thanks again, all

[Dog80]

@ZipperJJ

But, Dog80 says his pumps are accurate and they dispensed 2.5 liters more than the customer’s tank size…so I’ll believe that my station’s pump can dispense exactly as many gallons as my tank size, without assuming any funny business.

And there’s another issue. Suppose that I cheat and my pumps dispense less fuel than indicated. At the end of the fiscal year it will appear that I have sold more fuel than I have bought. Any bussinesses that deal with fuels are closely monitored by the government and this will instantly raise a red flag.

So it will take all kinds of creative accounting to rectify this problem, like fake invoices, having connectrions in the Tax agency etc. In my opinion, that’s a risk that only fly-by-night bussinesspeople are going to take. Any well-established gas station should be safe.

[Tim_T-Bonham.net]

@Mr. Slant

My friend at work, Ron, has an uncle who retired from Ford.
The old standard was that “E” on a Ford would be 2.5 gallons from dry.
Take that for what it’s worth.

It’s probably accurate, for back then, when they got about 10 miles to the gallon.

A friend who works at the Ford truck plant just across the river from me said that they try to calibrate the gauges for a gallon or a bit more after the “E”.

Both of those seem to allow for roughly 25 miles of driving past the “E”.

[lobotomyboy63]

@Dog80

And there’s another issue. Suppose that I cheat and my pumps dispense less fuel than indicated. At the end of the fiscal year it will appear that I have sold more fuel than I have bought. Any bussinesses that deal with fuels are closely monitored by the government and this will instantly raise a red flag.

So it will take all kinds of creative accounting to rectify this problem, like fake invoices, having connectrions in the Tax agency etc. In my opinion, that’s a risk that only fly-by-night bussinesspeople are going to take. Any well-established gas station should be safe.

A long time ago, I saw a bit on TV about a gas station that was cheating people. The pumps were programmed to run normally up to 10 gallons, IIRC…so if the posted price was $2.499 at the time, 10.0 gallons would cost $24.99. But at that point, it started charging double for each gallon over…11 gallons would run you $24.99 + $5, not $24.99 + $2.499.

The TV station videoed it, calculated it, busted them. Ever since I saw that, I calculate the gallons x cost per to make sure it’s right (ballpark, in my head).

[spinky]

I don’t understand all the speculation about pump inaccuracies, evaporation, conspiracies and fuel trapped in the lines. Isn’t the incredibly obvious answer that the owner’s manual specs on gas tank capacity are not particularly precise?

This may blow some minds, but a gallon milk jug holds slightly more than a gallon.