don't be too worried about fuel average, enjoy your car, at max one can get 1-2 km/l saving without going crazy,,,,
u can get above that using a few methods like rolling,,, say speed up to a good speed like 60-80 and let the car roll in neutral till u reach say 40, and then again speed up...
r keeping the rpm low and driving in 1000-1800 rpm range, (which can cause engine damage in long run).
a friend of mine used to do extreme with the rolling technique, he used to switch engine off while rolling, now when u switch off, the meter is off, the power steering don't work and breaks are also loose,,, once i traveled with him me in my car and he was driving his our start location and end was same with the same route and the total distance shown by my car was 32 km where as his meter was showing he traveled only 17 km ..... i was like WTF.... he traveled almost half the time with engine off. so basically you can go crazy of just spend a bit more fuel and enjoy a 1.5 million worth car u got under you.