I spent a total of 5 ours on mainly highway on cruise control at 60mph this weekend towing a 26 ft trailer holding my 23 ft boat - Im thinking about 8000lbs total. I got 11.8mpg on 89 octane. I am impressed. When I took the trailer off it was like finding another 4 cylinders and I got an indicated 18mpg for the next 50 miles - again cruise at 60mph all highway. I was planning to add a CAI, new headers and a new cat back exhaust system but now Im wondering if it would be worth the effort. Oh, by the way, my truck has 81000 miles on her....

 

If you are going to add all that stuff just to add mpg, don't do it! You will nver keep the truck long enough to save the cost of that stuff in gas

 

+1.