The far left vent on my 2013 Wrangler isn't as hot as the far right ot middle vents. Its noticeably cooler. Would a heater core flush help this? Maybe a reverse flush? I use the correct OAT coolant and thats all that been used in this jeep.
The tread pattern has to make a impact too. I have BFG mud terrains and I know when I switch to my summer tires it will make a huge difference in mpg. I only get 17 with the Rubicon. I'm sure it doesnt help that I have 410 gears too.