Originally Posted by RuggedExposure
This is much more important than knowing your mpg.
If you're searching for the best speed for mpg use a stop watch to time how long it takes to use a specific amount of fuel (.1 or .2 gallons). Most likely your best mpg will be between 2750 and 3000 rpm.
Having an OBD2 connector is great for more than just reading your MPG. Diagnostic codes from the ECU alone is worth it. May no longer need to find a dealer with a MOSS.