So I did a trip from Albuquerque to Phoenix last week, and i figured this would do for testing the mods out.. So the front of the power stroke was lowerd 3 inches and I built an air dam onto the bumper close to was Dave done but 2.5 inches off the ground, its 3/8th convayor belt material with no subframe yet.. So I depart Albuquerque and set the cruise control at 70mph 2k rpm and sit back for the run with a full fuel load. I took I40 most of the way and then the GPS told me to go through the National forest straight through the deep Rocky Mountains.. I decide to keep the speed the same and the cruise control on, never once did it down shift going up on the grades and it was running cool, I turned the AC on once I came out of the mountains because it was getting God awful hot out.. I roll in to Phoenix with still half the rear tank and 500 miles on the odometer, I also forgot to mention that I had about 75-80 miles on the odometer before even leaving from driving around town.. I was honestly shocked at that point in time so I kept driving around Phoenix (in town) untill I needed to fill up.. I called it when the gauge dropped to 1/8th or so tank and 590miles, so I got fuel, I took on 27gals of diesel for $3.49.. 22 Flippn miles to the gallon in a 97 F-350 CC Dually, you have no idea how awsome this is, ive never got this type of miles before, so now Im amped about doing the side skirts once I lower the rear down.. So after thinking about this, if there were no mountain range do you think it was possible to get about 24mpg out of this old truck and or even more with using no cruise control? Other things that I done prior to the trip was I removed my bug shield and removed my fiberglass full length running boards so I can start planning for the sheet metal/conveyor belt skirts, also I still have a sun visor on the dually also..