Fuel mileage meter

[ertert222]

Does anybody know how this really works? Does it actually measure fuel flow/amount compared to mileage ( which I would think should be pretty accurate with a good flow meter) or does it "fake it" and take a good guess?
For example comparing fuel tank level to mileage and averaging?
Dads Intercooler Tanks

[phoenixrhino2]

These are known as "Dummy Gauges" and your hand calc is more accurate..

[ertert222]

I understand that. I am trying to find technical details/operation how it works.

[walkeru08]

The mythbusters once tested fuel mileage myths and they had a Ford engineer helping them out. He said that the computer uses how much air is flowing into the engine to calculate fuel mileage which explains the inaccuracies. If it truly measured fuel flow it should be dead on. This may not be true for all vehicles but like I said they had a Ford guy and they were using a fairly new expedition to do the test is memory serves.

[2005F250]

If you reset the meter EVERY time you fill up it's pretty darn acurate. Mine is always .5 gal. below what my milage is.