Possibly stumbled into a 5 MPG increase, by accident?
 

Hello, recently I started a thread about having horrible MPG in my 2005 F-150 Lariat with the 5.4. It started after I put new mufflers on, installed Spectre CAI, and dropped tire size from 35x12.50x18 mud grapplers to 275/70/18 Kelly Safari's. I was pretty bummed because I replaced mufflers due to a busted chamber in one and bought some nice super 10s to replace. After I got those put on I realized the morons at the muffler shop welded them on backwards and I still haven't changed them. That weekend my Spectre CAI came in and I installed it. Within the next week I bought the new tires. All of a sudden my mpg went from 13.6 with 35's to 11 with 275/70's and the CAI. I was instantly thinking the mufflers had to be causing this problem. Still to this day I have not been able to get them reversed because I work 7 days a week. So looking at my 11 mpg everyday just really started to piss me off. So one day I was talking to my grandma and got around to cleaning her air filter. Which gave me the idea to check mine. It was dirty, not to bad, no mud or anything. So having this wonderful day off of work I took off my filter and soaked it with k and n air cleaner like I normally do nothing different so cleaning it would not be the solution. But this time I did change one thing. The Spectre CAI system has the box style around the filter to, I assume keep extra dirt out, Well I was in a hurry to take my Girlfriend out to dinner so I just leave the top, lid-like part of the CAI box off while leaving the side box in place. While waiting for the filter to dry I did my routine terminal clean and added 2 quarts of oil. So I leave to town which is a pretty hilly road and into town drove around town for a little while, usually my mpg would be already at 11-11.3. I didn't bother to look till I refilled and seen my MPG was at 16.6 after driving very hilly roads and lots of stop and goes in town for 3 hours. I literally jumped out of my pants since the last 4 months have been hell with this stupid 11 mpg crap. So, I'm no genius or a very good mechanic at all. But maybe the lid was restricting flow and causing the engine to work harder to suck through that tiny hole and resulting in horrible MPG that taking off that lid I may have stumbled into a solution or maybe it was something else, I would still like everyone who might have had a similar problem to try this and let me know if it helped. I'm not guaranteeing anything but it couldn't hurt to try. So let me know what you all think and if any of you try it let me know your results. Have a great day guys and hope this was helpful if you have this similar problem! :-drink