In city GP5 does about 14-15KM/L without eco off and drive like a maniac. like me :D . If you can control yourself, you can easily get 20+. I am driving around, Pitakotte, Rajagiriya, Nawala, Nugegoda and Thalawathugod FYI.
Even in "S" mode From colombo to Bandarawela, it does 16KM/L. Thats...