Sentra ATs kinda suck... and it'll also depend on your engine and driving habits. If you're used to the pull of a 1.6 manual and you're driving a 1.3 AT, get used to horrible mileage. If you know how to max them out, it's not that bad, but still, a 1.6 AT can get 6-7 km/l in bad traffic. Especially with the super-powerful aircon on those things.