Re: Tire size affecting mpg.???
Of course it will make a difference. Also if the tire is Low Rolling Resistance or not will effect it too.
The 2014 OEM 18" Tires are very good on MPG. I don't know too much about the 20's but I expect they are similar.
Not sure if Jeep used Low Rolling Resistance Tires in 2011. I don't think they did. The 2013 Dodge Dakota "Take-Off" Wheels I got had the same tire as the Jeep but were not the Low Rolling Resistance version. But they have a much higher wear rating.
08-10-2014 Limited 3.6L Red W/Black Int, Tow Group IV, 8.4AN Radio, ProClip, OBDLink/Torque, Zeigler Lifetime MaxCare
OEM: Mud Flaps, Matts, Cargo Liner, Cross Rails
UConnect: 13.48.3 TSB: 21-007-13C (Yippy) Tires: OEM/Nokian