Page 196 in your Owner Manual explains that ECON displays the MPG, SINCE THE LAST TIME it was reset. That will include any idling or acceleration, Whe idling you are registering 0 MPG.

https://cimg3.ibsrv.net/gimg/www.che...a8bfc6c9d8.png

I'm confused: economy it's how much u saved; MPG - how much u spent. Should be....
so can I reset it before highway trip and it will show me almost real MPG?

Or, rest it when you get to speed and observe it when you start to slow down. It gives you the Average MPG (fuel economy).

It should measure/count a fuel flow and wheels spin - not an idling

Maybe it should, but it doesn't.

are u 100% sure?

YES, Idling does count as 0 MPG which will affect your readings. The same goes for coasting, but the opposite. I have seen 77 MPG but was coasting downhill at the time. So what you see is the average from the last time it was reset.

Funny thing. I'll throw my 5 speed in neutral and coast when coming to a stop sign or red light. I see 99 MPG a lot. I think that's the highest the computer will show.