Help How DO I Achieve 15mpg on my 2012 That Everyone Gets But Me? Noob

[00Silverado4x4]

Every once in a while I'll hand calculate vs DIC readings. They've always been off by ~1mpg with all city driving. When I do drive highway consistantly it tend to be a lot closer if not dead on to each other. Only driving 7 miles to work with 4 red lights and a thousand "smart" drivers really kills the mileage. Still can get anywhere from 17-20mpg on the highway dependent on speed and what I'm hauling with me. Not too shabby considering age, use, abuse, mileage of the truck and my bad driving habits. Still rocking factory plugs.

[Jsdirt]

My DIC reads 14.1 right now. Hand calculated it's 16.3 last fillup.