Mpg computer?

I got a fancy pants Pioneer head unit and iDatalink module that plugs into the OBD port. Gives me a real-time instantaneous MPG as well as average (since last reset) MPG readout. Admittedly I rarely sit down and do the math myself but it seems to be relatively accurate without manually entering fillup amounts.

 

Like this? my dad had a little book in his celica to record... i do it with all of my trucks, but now i use my phone... just so i know

 

I do something very similar.
Mpg in parentheses is trucks calculation. The other mpg is calculated old school. I also have notes if I was towing and also when I added KDMax.

 

For whatever it's worth, I normally just use a calculator for my 2013. It's pretty consistent (about 25-26 mpg mixed), so I do it mostly to track if there's any sudden downturn or progressive reduction that might indicate problems (like a lazy O2 or something).

That being said, I recently got a Panlong OBD dongle (actual product - not trying to push this thread into humor territory) because it's one that is compatible with the Dr Prius app that can give readings on all the individual cells in my wife's Prius.

When I poked at it in the Taco using Torque Pro, I noticed one of the available monitors was for MILES PER GALLON! So I tried it - not sure exactly what parameters are being monitored (I assume one is actual fuel consumption as monitored through the fuel system), and it was way off from my usual calculations (I recall about 30+ mpg), but I never entered the Taco parameters into the Torque App before. Once I entered it, it was a lot closer, but I believe my own calculations more.

It did come in handy when I wanted to know which, between two different routes with roughly the same miles, used more fuel. I was able to at least determine which way used less fuel (taking the avg mpg given and extrapolating based on the actual miles) consistently even if the ACTUAL mpg was not correct. So it is useful when trying to compare something.

 

Forgot to mention - the avg mpg reading is apparently a "trip" reading (ie. shutting the ignition off and restarting resets the figure to zero.

There is also a PID (that was available and I did try) for ACTUAL (on the fly) MPG calculation, though I don't know how 'off' that one is.

Also, some of the data I punched in to Torque about my Taco was just data I was able to find on the internet, so I don't know how accurate it COULD be if everything was entered correctly.