My honest opinion is the Average MPG and Instand MPG is BS.
I did a 660 mile trip to Cali for a F150 meet few months back. It showed I averaged 14.7 mpg, filled up and hand calculated it. 14.3 mpg. It always shows high.
My truck showed I averaged 14.8 mpg my last tank. I hand calculatd it, it came out to 13.4 mpg.
I filled up, went offroading.. mashing the gas, having fun. Showed me 13.4 mpg, got on the interstate (75mph speed limit) it jumped to 15.9 - 16.0 average mpg. It's never been over 15.8 mpg average except GOING to Cali it showed like 16.6 mpg and dropped constantly to 14.7 - 14.8 mpg doing the same speed for atleast 200 - 250 miles at a time to each gas station.
The slower I go, the worse my average mpg shows. Harder I drive it, the better it shows..
My tires are stock size, stock gearing. So it shouldn't be off.
Sitting at a light it will drop from like 14.8 mpg to 14.4 mpg just idling. Or cruise control doing 70 mph and I gun it to pass someone it drops like 3 tenths..
I keep forgetting to change it to another parameter. Watching it is silly.