I just bought a 08 1500 4x4 Sport w/ the 5.7L HEMI! This is my first gas truck in many years. What kind of gas mileage can I expect to get and what are some maintainance things that I should do in order to get the max life out of the engine. The truck currently has 90K miles on it.

 

Sticker for that truck states 13/17 but you'll get lmore of 12city/16highway

Oil change by book is 5kmi but this should be done if your highway driving IMO. do every 3kmi for city driving. 5w-20 ONLY! Otherwise you'll have issue's with mds activation. It's oil weight sensitive.
plugs due every 30kmi(basic coppers)
Front&rear diffs due every 30kmi or every 15kmi if towing
Coolant every 5yr or 50kmi whichever comes first.
Trans fluid should be done every 50kmi and the filters aren't due till 100kmi