Gas pump miscalibrated?

[1993CivicVX]

I have a 10.0 gallon tank. But 10.1 gallons of gas was pumped into it without topping off. Is there reserve on my tank? Isn't it really hard to put as much gas in the tank as the tank size is? Has that ever happened to you?

It seems really unlikley the gas station would have a miscalibrated pump. But it also seems really unlikely I was bone dry. I know TomO reported a tank of 9.9 gallons. But that seems reasonable since it's still below 10 gallons! And I wasn't driving for that long with the needle below E. I was thinking there was still a gallon left in the tank. I may bring a 5 gal. gas can today and compare the Getty station where I suspect malpractice and the Gulf right across the street that never has given me a suspicious fill up.

I'd really like peoples' feedback on this one. Tell me I'm crazy if that's what you think-- just some feedback. Thanks!

[SVOboy]

You can fit a lot in the filler neck and ****...I think tanks tend to seem a little bigger than they're reported...I've never run my car down that much though.

[trebuchet03]

Fill neck

[baddog671]

I dont know about the civics, but I know the fillneck on my metro is huge. I took it off once and its about 2" wide and 12+" long...

[1993CivicVX]

don't you have to top off to fill the filler neck? When filling up my car, the pitch of the sound from filling the tank doesn't rise that much toward the end. The last two gallons it starts to rise somewhat and then it stops without really going up really high like on some cars. Anyway, I'm gonna test it soon! Seems unlikely that station is miscalibrated, but only one way to find out.

[trebuchet03]

don't you have to top off to fill the filler neck?

That depends on how sensitive the full tank release mechanism is That's why I always fuel up at the same station and use the same pump

[1993CivicVX]

Well, I did the test! There the same. Surprise surprise. However, the Gulf pump is more sensitive to cut off than the Getty. In other words, the Getty pump allows me to fill to the absolute limit much easier than the Gulf pump. So i think I fill up at the Getty from now on. But I really felt like I was getting ripped off!! Oh well.

[rh77]

A lot of pumps, despite your region of North America, depends on the gas station franchise's aggressive use of vapor recovery. I've filled-up from Boston to LA and it differs where it cuts off -- or even how far it lets you consistently try to fill completely into the filler neck.

Some places allow a compete fill up to the brim...

Others have the "elephant trunk" system with aggressive, spring-loaded gas fillers to recover the vapors emitted.

LSS, both mandated systems (depending on local regs) can give you a different total fill, and different final, calculated FE.

The questions becomes: is the SG a better estimate of FE or fill-up???

RH77

[1993CivicVX]

yeah, I suppose the best estimate is too fill at the same pump every time. Which is what I'm gonna try to do. Or at least have the last fill up be at that pump which fills to the very top, then you know your mileage is at least not worse than whatever you are getting. So it might not be accurate for every tank, but for several tanks will give a very accurate overall average. I'm still baffled how my 54mpg tank was so low. Really puzzling.

[derangedrover]

that's one advantage on my range rover, 1/2 a gallon on a 23 gallon tank doesn't affect FE much, whereas 10 gallons vs. 9.5 affects it quite a bit more!

:P

[trebuchet03]

The questions becomes: is the SG a better estimate of FE or fill-up???

Fill-up On an individual tank - it might not be accurate... But, for running averages...

[Gary Palmer]

I don't think the gas pump is miscalibrated.

When I replaced the fuel pump on my 89 Civic Wagon, I had it totally empty. I put 2 gallons of gas in, to get it running. Then I went to the gas station and put in an additional 9.8 gallons. The tank is only supposed to be a 10 gallon tank, but I think that is really for the sake of the gas gauge and the fact that you have to have some fuel sloshing in the tank, for the pump to be able to even pick up.

If you wanted to haul a couple of gallons of gas, in the car, you could run it out and then see how much the tank will hold. I'd guess that it will hold 11, maybe 11.5, if it's really low.

[Ryland]

gas pumps are not alwas accurite, any idea how much gas you had left in your tank? I've put over 10 gallons in my 10 gallon gas tank befor, but it was pretty close to empty, so it seems possible, but we've also put "14" gallons in an 11 gallon tank, and the gas gauge said it was only 3/4 full, and at that point, with a little arguing with the gas station they only charged for half.

[itjstagame]

Also, 'supposedly', I've heard to fill up in the early morning or late night because that gas is more dense. That is 'supposedly', 10 gallons of cold gas (at night) when warmed up (during the day) will actually be more than 10 gallons.

I'm not sure how significant this is, being a liquid and probably only the difference from at most 40-50F and 100F I can't see how the gas can really change in density that much, but I've seen that suggestion on more than one site... so not sure.

Anyway, my point is, if it was 100F out and 1pm, then maybe you pump 10.1 gallon of gas, but maybe it was only 9.9gal cold?

[1993CivicVX]

Originally Posted by Ryland

gas pumps are not alwas accurite, any idea how much gas you had left in your tank? I've put over 10 gallons in my 10 gallon gas tank befor, but it was pretty close to empty, so it seems possible, but we've also put "14" gallons in an 11 gallon tank, and the gas gauge said it was only 3/4 full, and at that point, with a little arguing with the gas station they only charged for half.

holy ****, that's crazy. They're charging only half is admission of guilt. I checked the gas station and it wasn't miscalibrated.

[trebuchet03]

Originally Posted by itjstagame

Also, 'supposedly', I've heard to fill up in the early morning or late night because that gas is more dense. That is 'supposedly', 10 gallons of cold gas (at night) when warmed up (during the day) will actually be more than 10 gallons.

I'm not sure how significant this is, being a liquid and probably only the difference from at most 40-50F and 100F I can't see how the gas can really change in density that much, but I've seen that suggestion on more than one site... so not sure.

Anyway, my point is, if it was 100F out and 1pm, then maybe you pump 10.1 gallon of gas, but maybe it was only 9.9gal cold?

That's air temperature The fuel is stored in very large tanks (think 10K gallons) underground where temperature is much more stable. Daily temperature swings won't raise the tank temperature significantly. There's a thread somewhere on here with some calculations - I think it was something like 9 or 10 gallons over a 50 degree difference for the entire 10,000 gallon storage tanks