Okay so a little history for those of you that want to know it all! My truck is an 09 F250 cc/sb 4x4 with 3.55 gears. It is my company construction truck. I bought it new about 9 months ago with 67 miles on it, I now have 25300 miles. I am an extremely anal person and document/test everything I do. I wanted to give the truck some time to make sure all bugs were out and I would know exactly how the truck feels. The truck is bone stock with a K+N filter and Amsoil (which I run in everything I own). With this setup I would average about 13mpg in town and 17-18mpg on the interstate both unloaded. And yes....I hand calculate every fill up and I also always get fuel from the same place and same pump and park the same way, just to make sure all my data is accurate. Actually if you do fill up this way you will find (at least my truck is) that your lie-o-meter is pretty accurate. I also through oil analyzing have found, that my truck would end up with around 4% fuel dilution by 4500 miles which for me was all I would allow. So I have changed my oil every 4500 miles $$$. So at 24,900 miles I decided it was time to get rid of the truck killer and start deleting (I wish I knew an epa guy they all need there asses kick, dpf is about the dumbest thing they have ever come up with). So I pulled the truck in the garage, I live in Illinois and right now we have been having single digit temps outside. Due to the temps I had been letting my truck idle more so my "lie-o-meter" was reading around 11.4 and had used about a 1/3 of the tank of fuel. I changed out the pipe (not bad, did it myself on my back), down loaded the tune (River City Diesel's 450hp economy/tow tune), and changed my fuel filters. Like I said early, this is my company truck so power "was not" my main goal. The next day I left the house (0 degrees) and started my day like any other, drove around town to different jobs and supply houses and left truck idle like the day before, but this was not the same truck!! It was better in every way: it ran smoother, it shifted better, it got better mpg and yes had tons more power. By the end of the day my meter had climbed to 14 mpg (I did not reset it yet because it was the same tank of fuel). Today I was going to be on the interstate for most of the day and I was on empty, so I filled up and reset everything. I guess I should also say that I run Fords additives in my truck. Anyway I put about 150 miles of interstate and a little in town driving on the truck today. My first 40 miles were all interstate and I was getting 23.5 mpg and by the end of the day with a little in town driving I was getting 21.5 mpg. I was traveling 74-76 mph on the interstate. Also now I will extend my oil changes to around 25000 miles saving me tons of money. I Love the truck even more than I did. A BIG thanks to RCD and SCT! The truck barely even smokes on full throttle either. This is the truck Ford thought they were making before the epa jack offs got involved. Anyway sorry for the long description but I like to be thorough! If you are on the fence about delete and tune do it....with how much better the truck is, I don't even care if they try and void my warranty. Hope this helps some!