Fill fuel in the coolest hour

[ksa8907]

Originally Posted by UFO

Like Charlie mentions, the fuel is stored underground, so it doesn't matter what the outside temperature is, the fuel is dispensed at virtually the same temperature; fuel density vs. temperature is moot.

I agree, and more to my point regarding "negligible differences", even a 20 degree swing is not enough to be noticeable at the pump.

If my math is correct, roughly 2.6% change between 68f and 104f.

If that is linear, 0.07% per degree(F). Realistically, the metered fuel temperature my vary by up to 10 degrees (guess), so maybe a 0.7% inaccuracy IF there is no temperature correction being done on the fuel volumes.

Larger fuel purchases will diminish the inaccuracy as only a few gallons are stored above ground at the pump.

[rmay635703]

Up to 3 gallons of fuel is in the pump and hoses above ground, so it may make a small difference.

[ksa8907]

So, maybe there is another reason for filling at the same pump, to rule out accuracy differences in the metering.

[roosterk0031]

Find the pump that gets the best calculated MPG and stick to it, at least till they fix it and then look for another.

[gone-ot]

Some reading material: http://www.consumerwatchdog.org/reso...lUSAJune07.pdf

[Hersbird]

A problem I could see is if you really topped it off on a cold morning, from a cool underground tank, then drove a mile home and let the car sit for a few day's with a big temp increase, what happens to the surge volume in the already full tank?

[UFO]

There is a reason the fill nozzle clicks off before the fuel is all the way up the neck of the fill tube. Best to leave head space, otherwise that fuel gets forced through the vapor system into your engine. Big waste of fuel.

[oldtamiyaphile]

Originally Posted by Hersbird

A problem I could see is if you really topped it off on a cold morning, from a cool underground tank, then drove a mile home and let the car sit for a few day's with a big temp increase, what happens to the surge volume in the already full tank?

I used to drive a van where the fuel tank was located directly behind (and was therefore heated by) the engine.

If you filled it quickly on a hot day, the pump would click off and fuel would then continue to run out the filler as it expanded.

This suggests that the fuel coming out of the pump is quite cool even on a really hot day.

[ksa8907]

This makes me want to put a temperature sensor in my gas tank.

[roosterk0031]

Underground tank is double wall, might take days for temp to equalize. First thing in morning at least pump is cold, pump as slow as you can. Even though I don't think that will matter.