Gas pump miscalibrated?
 

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!

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.

Fill neck ;)

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...

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.

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 :p

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.

Region vs. Vapor Recovery
 

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

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.

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