what is the formula to figure out gas mileage?

[Blondebaerde]

Originally Posted by IShootNikon

Or use an app if you don't want to figure the math

Y'know, it's funny: the other year I bought an OBD II plug for my '07 Tacoma, to read some of the fault codes. It was throwing one that turned out to be minor, but the experiment was interesting anyway.

That connects via Bluetooth to my phone, and an app that was either free or a few bucks on the Play store.

One value calculated is mileage. Interesting the data is there, but Toyota chooses not to surface it through the dash electronics, of which there are (very) few. Maybe it's that simple: why give up data through complicated UI if no one demanded they do this? Hence the difference between "utilitarian" (Tacomas) and "luxury" (for example, a modern Cayenne truckster).

I haven't done a detailed comparison, but as I *recall* that OBD II plug was providing accurate mileage: manual calc, my truck averages about 17mpg around town with usually-infrequent freeway time. If more of the latter, it goes up to about 19mpg. Ok, if not great, for a 10 y.o. supercharged four liter V6 I figure.

[WyoNewk]

Originally Posted by Labonte18

There should also be a difference between temps.. I'm not positive about this, but the hotter it is, probably the less fuel the tank holds due to vapor bubbles and the like. Someone who knows more about the properties of gasoline can likely give a definitive answer..

I'm not that guy (who knows more about the properties of gasoline), but sure, fuel expands with heat, just like most things. With elevation too. Some airplane race pilots will refrigerate their fuel before filling the tank just before the flight (or simply fill from the cool, underground storage tank), then fly low to burn off some fuel before it warms and before climbing higher where it expands due to less atmospheric pressure. I can't recall how much difference it makes -- not much for most of us, but for a racer any slight advantage....

[AlaskaErik]

Originally Posted by North Beach Person

I press a button on the steering wheel.

Expect a very inaccurate reading. Every vehicle I've ever had shows MPGs to be higher than actual. When I divide miles driven since last fill up by gallons just put in tank, I always get a lower number.