With the Eco's and towing, it's a lot about the amount of boost and rpms that will help. Running Premium does help when towing. You have to let the engine run at least a full tank so the computer can adjust for it, so just don't think you can toss a half tank of it and expect to see results. (I learned that myself)
Running on the flats, the turbos like more rpm's then boost. More boost, more gas. If you can monitor your boost psi, you will see that you will run more psi at lower rpms to maintain a given speed then running some 500 or more rpms higher. The engine will also run cooler too.
I'm getting an average of 10 mpg's towing my #7000 TT. I live in the NW and go over the passes to eastern WA all the time. Lots of flat, lots of grades, lots of downhill runs.
The smaller 2.7 puts out good power numbers, but it also needs more fuel to get to those numbers. Just like the 3.5.
I monitor my ODB2 sensors with a simple plug in and phone app. Gives me a ton of info that I didn't know before. Adjusting my driving and monitoring the temps, boost, etc, has made a big difference in towing my heavier TT.
Good luck! mitch
