How can I calculate MPG using an OBD-II Device

• Mass Air Flow (PID 0166)
• Fuel–Air commanded equivalence ratio (0144)

Can these be used to calculate the actual fuel consumed?

Is the output correct?

This is what I did for my 2003 Opel Agila.

Firstly, you need an android device. Mine is a Galaxy S4.

Firstly, go onto eBay and search for an ELM327 reader, it will come up with lots of OBD-II readers for a few pounds/dollars. Make sure you click the UK Only box, or whatever your country is so you don't have to wait years for shipping. Then choose the price + P&P, lowest first option. Then go to buy it now, unless you can wait for the auction to finish.

This is the reader that I purchased. I cannot say if the any other ones are any good from my personal experience, but this one works really well, and I bought it in an eBay auction for like £2.

Now you've bought one, you need to go onto your android device, and go onto the Google Play store. Search for dashcommand, and download this app:

Make sure you download this exact one and watch for any other apps with similar names. I have tried several and have found Dashcommand to be the best one.

Now, open dashcommand, and set up your car. Connect your OBDII interface, and set up:

Choose ELM:

Enter your displacement. You can find this on wikipedia if you search for your car.

Now press the Not Connected button, and wait for it to connect. Then choose dashboards:

Now choose the picture of the fuel pump

Now I am not connected, so nothing shows up. This updates about every second, and tells me my MPG over certain time ranges, and my average over every journey (which is saved by the app, so it remembers every time you open the app)

I think this is quite accurate, but my 2003 Opel Agila does not support range calculations, but it seems to tally up that I get 40mpg, and get about 330 miles per tank.

• How would it calculate the MPG just by knowing the displacement of the engine if the related PIDs are not supported? – I have no idea what I'm doing Apr 6 '16 at 8:00