I have an Overland V8 4x4. I average an honest 19 mpg (hand calculated) commuting 50/50 city and highway. I don't get on the gas a whole lot. I've learned to feather the throttle when on level ground or going slightly downhill. I have the instant MPG display on the upper right of my EVIC display and I keep an eye on it to monitor fuel consumption. I also coast to stoplights etc. I notice most people driving around me are in a hurry to get to the next red light. It's funny. I also try not to use the brake unless I have to. Slowing down for no reason is wasting gas, as you have to accelerate again. Again, I see people around me hitting their brakes when going down a slight incline, even going the speed limit, and with no one around them. Leave your brake pedal alone!! lol
Considering all this, I might have been happy with the V6. But driving thru the mountains and being able to pass 3-5 cars without thinking about it on a two lane road are some of the reasons I got the V8. Plus it's very smooth and moves the Jeep effortlessly. In my book, I'd rather have PLENTY of power when I want it, rather than regretting not having enough power. If I have to pay a 1-2 MPG penalty for that power, so be it. It's worth it to me.
I had a 2004 Toyota Tacoma crew cab with the V6. It got 17-18 mpg on a similar commute, except it was about 7 miles longer freeway driving. It was as gutless as can be on the freeway. It would downshift out of overdrive on the most insignificant incline, or a 5 mph headwind. I got rid of it after less than one year.
I tried using ethanol-free fuel for a bit. I got about 30-40 miles more per tank using it. Ethanol-free fuel seems to be catching on a bit around where I live, and the gas station has jacked up the price accordingly. Now it's not cost effective at $.42/gallon more than 10% ethanol 87 octane, so I'm back using the junk gas lol.
Here's a pic, going 65 MPH on a flat Oregon freeway. Almost 25 MPG, for a 5000 lb ride with 360 HP. I can't complain: