redline is like what 6k on that motor? 5k shifting isn't going to hurt it, if you bounced the needle all the time then that's different but it sounds like your driving at about 75-80% throttle. Your fuel economy is going to vary from the epa ratings, I have found that honda tends to rate thier cars lower than what you can get. A b16 imported, driving highway and city, 6k shifts (redline at 9k), and 33-35mpg....I doubt it was rated that high when it came out....even in the del sol in the 90's. My 01 civic was rated at like 36/40mpg city/hwy and I would get 42-45 if it was all hwy and 36-38 with a heavy foot and combined city/hwy. Then my 93 hatch got mid 30's and I drove it like I wanted a new engine.

Chances are your "friend" is used to v6-v8 motors that do need to shift at 3k and get oil changes evry 3k miles....not the 4cyl with a power band that starts a 3k and the sevice manual goes 5-10k between oil changes.