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How **MANY** gallons?


I pumped gas one day. The pump was slow… I thought, I’ll top off to know how close I was to running out of gas!

I have a receipt that says I put 25 gallons in a 20.4 gallon gas tank!

Please explain!

You need to ask the station owner this question, or your state’s Consumer Affairs Div, or the state agency that checks and verifies gallon measures for this product. We can’t explain it with any theory. I can’t believe any tank fill can be off by 25%.

Are you sure your tank max is 20.4 gallons, for sure?

Okay, whether the clerk believes me or not, I am not crazy. I got the DOT to come out the next day and check the pump, and he said it was “within tolerable range” and that “there is a one in a million chance something could have happened”. I have a 20 gallon tank with .4 gallon over-fill capacity. The clerk thought I stashed a gas can in the back of my car!! And, I always enter a gas station on fumes, so I have ALWAYS gotten just 18.5-19.7 gallons of gas.

OK, you don’t say what state you are in. I have heard that the vapor recovery systems on California (and possibly other states) gas pumps will allow you to pump slowly and it will keep sucking the excess gas back into the pump. Apparently this doesn’t happen if you have a fast enough flow going, but you said it was pumping slow.

I don’t know how true this rumor is. I have just heard it, so anyone with real information please correct me if I’m totally wrong here . . .

I’m in Alabama. Funny thing is, I told the girl beside me my pump was pumping slow… and she said, “oh, well I just moved here from California, and thought everything here was that slow”. ha

The system is designed with a buffer so that people who run to “E” don’t destroy the pump.

Now, what in the world possesses you to run the tank so low?

“I always enter the gas station on fumes.”

That is not a very good way to go about things, and can cause problems with the fuel pump. Regardless, I suggest the tank holds more than you think, which is why you haven’t run out of gas. Yet.

Now that you know the tank holds 25 gallons you will drive further before refilling.

Yes, you will.

Good luck.

Please don’t complain when you are stranded on the side of the road, at night, in a thunderstorm, in a bad neighborhood, because you thought you could drive your car on “fumes.”

What is the year, make, model of you vehicle…

It could be, that as designed, your gas tank would hold 20.4 gallons. One cubic foot is 7.5 gallons U.S. Your tank volume is 2 3/4 cubic feet. If cube shaped, it would measure (roughly) 17"w x 17"L x 17"d.
A 25 gallon tank would measure (roughly) 18"w x 18"L x 18", if cube shaped.
As you can see, the dimensions aren’t that different for a 20 gallon tank and a 25 gallon tank. Also, remember that a container, with flat sides and bottom, will bulge to some degree with filled when a substance (in this case, fuel). So, it wouldn’t take much bulge, and an expansion allowance, for a 20.4 gallon tank to hold 25 gallons.
Finally, could your gas tank be rated for Imperial (Brit) gallons, and you filled it with U.S. gallons, which are smaller?

Pump calibration can be off; try the same thing at another pump I used to go to a certain pump at a particular station that read a little short when I filled my 5 gallon container but not as much in error as you state.

Don’t forget the filler neck. I didn’t see the vehicle specifics listed yet but many vehicles have fairly significant neck lengths. Topping off completely includes this volume and all of the errors you’ve cited already.