If most of your city driving is a speeds below 60kph, you might even try shifting down to '4' on the EVIC. I noticed this improved my city mileage, and further improved the overall responsiveness of the truck, as it never sees an OD gear.
BTW - The numbers on the EVIC don't follow the gear numbers exactly.
1 = 1st
2 = 2nd
3 = 2nd Prime
4 = 3rd (Direct)
5 = 4th (1st OD gear)
When in 'Drive', you also get 5th gear (2nd OD gear), but you have to contend with the MDS as well.
Also, for piece of mind, you can (within reason) run in any manually selected gear, or in tow/haul mode without worry of hurting anything. For the sake of experimentation and to see what it's like, I would run for a while using the tow/haul mode. You will notice that it shifts a little differently, and decelerates harder, and is more responsive. Some find these characteristics annoying when there is no trailer in tow, some find them desirable.