[titanman2789]

Be thankful your doing that well. Mine is way worse after level and 35s. The claimed mpg is pretty much unattainable, Makes me think I should have gone with the ecoboost I was looking at

I have 1400 miles on my Express Quad Cab. I have gotten 12.5 mpg on every tank except for one - 13.9 - where I had a lot more highway than usual. Most of my driving is city and I let my truck warm up for at least 5 minutes on every cold start up. So I'd say I'm doing ok. Sometimes I think maybe I should have gone with the ecoboost but then I see those annoying Ford commercials on TV and see how ugly that truck looks. It doesn't do THAT much better, and the cost of ownership on that truck will probably end up being more in the long run with maintenance.

To the OP - I would think that first, you should use 89 as recommended in the owner's manual. Second, maybe not fill up at 7-11 but rather a better quality gasoline brand. I know the truck will run on 87, but if 89 is recommended, there is probably a good reason. Engineers could probably find a way to make cars run on peanut butter and jelly sandwiches but it doesn't necessarily mean you SHOULD