I can share my experience with the 9gen SE+ tourer.
Recently switched from the 205/55 R16 to the 225/45 R17 and was wondering how much MPG have I sacrificed by doing that, but can't get a solid answer.
The most I've seen on the display was 67 MPG, that was with cleared trip meter and full tank, when the number seems to be most optimistic.
Long term (since I got the car which is not that long) - I'm averaging 60.3 on carspending.com
, while on the screen it's stating 62.5.
Cruise-wise I'm floating between 72-77MPH - purely on the motorway and the only relieve is, when there is a road-work section and then I'm stuck to 50MPH, then the MPG climbs up.
I've tried the Econ button a few times and can't find too much of an advantage, other than seeing the different color on top, while pressing more on the gas pedal ..
The tyres are all on 38psi - I personally prefer them slightly firmer than suggested, and recently upgraded to Honda Green Diesel Oil (if I'm not mistaken - it's 0W-30 grade), from the previous owners Mobil one 5W-30 ...
New Honda Air and Oil filters.
Don't get me wrong - I've upgraded from 8gen 2.2 and just shy of 50MPG to this tourer 1.6 and 60+ MPG which is a 20+% gain in economy.