On Thu, 20 Jul 2017 08:50:37 -0400,
wrote:

Weighing the fuel is NOT required if the tests are done at the same
temperature - which would be a requirement for accuracy in fuel
mileage measurementin any case due to the difference in air density.

Being the progeny of two PhD chemists, I'm well aware of density, but are
you sure every mom and pop who "claims" their spectacularly "accurate" 22.9
mile-per-gallon numbers understands what you and I both know?

Do they realize that you have to keep the *entire* test at the same
atmospheric conditions, and where the typical mom and pop doesn't do that
for an entire tank of gas (which might take a week to use up during which
time the atmospheric conditions change greatly).

Do they even know what "test conditions" they're testing and do they run
"controls"?

Point is, my assertion (as yet unproven) is that the mpg figures with a
decimal point in them that people "say", are an indication of their
ignorance of what they measured.

As for what accuracy "can" people measure with the typical tripmeter
divided by pumpmeter test, I opened a separate thread on that topic because
it's a valid question (where I added the science & car guys).

https://groups.google.com/forum/#!to...ir/PT3YdPClM7g
What is the realistic accuracy & precision of typical consumer MPG
calculations (tripmeter miles/pump gallons)