I make frequent trips from Tennessee to Indiana. It's 273 miles one way. I made several trips before I installed an axel back. Best mileage I was able to get was 27 mpg. I just made a trip there recently, the first after installing the axel back, and to my surprise when I got 29 mpg. I'm sure there are other factors involved, but it sure put a smile on my face.

 

Nice, maybe more exhaust flow means the engine isn't working as hard? Lol.