Just turned 17000 km on my truck and it is slowly getting better on fuel mileage....did 164 km trip on highwy at 109km/hr..took a pic of what my evic said, then fueld right to top again, and handbombed the figures and was within a half mpg (uk) so was impressed....
figures:
164 km (102 miles roughly for u.s. people)
11.3 km / 100 km
which was 20.6 us mpg

20.6 us mpg = 24.7 canadian mpg

Hand figured after filling was 24.2 mpg at 109km/hr on a 164 km trip...

How are others doing...I wanted to put on level kit and bigger tire, but with price of gas..think I will run these tires (I put new good year silent armour on at birth) til they are done and hope gas goes down in future..ya right!

Also have truck tarp and bull bar with lights on this truck....not sure which helps and which drags or both...lol...

 

I did a comparable trip (650miles round trip) last week. I got 20.4 USmpg at 60-70mph using 89 octane fuel. Returning, I got about 19.0 USmpg using 87 octane fuel.
QC Hemi with 3.92's.

 

I am 392's as well and am using 89 octane....window sticker said 10.8 L/100km...was surprised how close I got to that!
Nice to see what you got on a longer haul too!

four weeks ago I was at 18 and 17 L per 100 km!