How many kilometers can I make on a Dodge Magnum RT?

Mr. Magnum questioned:

Ciao, I plot to hold a 2006 get out of Magnum RT sometime next month.
I only handbook in the city, and I’m wondering how many kilometers can I make on a Magnum RT; maintenance in mind that I only do city driving.
Also, what is the best way to keep up the best fuel efficiency, what driving problem must I adopt? Maintenance it below 3,000 RPM when accelerating?
Delight help, be grateful you.