13.5 km/l is pretty good for your class. Is that a one-time
figure or lifetime average?
For saving fuel, unfortunately most of the touted "fuel saver"
products are bullsh**.
Next to your initial choice of car (factoring in the weight,
aerodynamics, engine size, transmission efficiency, etc.), the rest
of it lies in your driving habits and maintenance practices.
Full throttle starts or take it easy? Slam brakes or rolling stops?
Treating the roads as an ongoing open-air street race, or playing
the entirely different game of trying to achieve maximum
efficiency?
For me, the trick on my EK3 is to get the Econo light to turn on
and utilise 12-valve mode (VTEC-E) for as long as possible, and to
try to use "VTEC Stage 3" as sparingly as possible ... 
Maintenance? Well that includes all the boring but important stuff
- engine and transmission oil, checking the battery, tyre
pressure.
