Re: KPack

Posted by DavidPackard On 2021/11/30 13:24:17

Gasoline Riddle

Kevin: Here’s some text on the subject of gasoline coming out of the tank filler.

Thermal Expansion of Solids and Liquids | Physics (lumenlearning.com) and
Volumetric Expansion Coefficients Liquids (engineeringtoolbox.com)

Now the specifics that are likely applicable to your case, I’ll use 20 gallons for the size of the fuel tank.
The expansion of gasoline is about 0.00053 per degree F, I use the phrase ‘about’ because that value varies by batch and blend. The calculation would be: Volume change = 20 * 0.00053 * delta temperature (F) . . . the resulting value would be the expansion of the fuel in the tank in gallons.

With a 10 degree change in temperature (of the entire gasoline volume) the expansion is approximately 0.1 gallons. All of this is quite linear, so if your fuel went-up 30 degrees the expansion would be about 0.3 gallons . . . more than a quart!

If the filler neck is 2 inches in diameter the vertical rise in the filler tube would be about 7 inches with a 0.1 gallon change. That too is a linear calculation, so you’re looking at about 21 inches at 0.3 gallons. We will have to deduct the amount of fuel that was used to drive back from the gas station. If the gas station is within 5 miles of home, my bet is the fuel spill is nothing more than the physics of expansion . . . nothing you can do to stop that, so drive the car about 15 miles after you fill-up for the last time in the Fall.

I find this happens every time I come back from the Grand Canyon after stopping for fuel in Flagstaff. We make that trip in November after the ‘summer rush’. At that time of year the average temperature in Flagstaff/GCNP is about 30F, while when I refuel in Phoenix the next day the temperature will be somewhere between 70 – 80F. The car has a 42 gallon tank, so there is a possibility of gaining about 1 gallon from expansion . . . I can see that amount of change in the computed gas mileage.

dp