Actually fuel average strongly depend on your fuel quality. A good quality fuel give you 1.5 to 3 km better average than normal quality or mixed fuel. I personally got 2 km improved average on good quality pertol (my honda civic 2006 model, which was normally given 8.5km/l, improved to 10.4 km/l after switching fuel within city. On motorway, I myself got 19.8km/l average at 85 to 90 speed, 17 km/l at speed 90 to 100, and 12.5 to 14.5 km/l at 120 or above speed. This all calculated figures are 100% correct and each figure calculated on fuel tank top up in civic 2006). I know all about this because I work in an oil refinery, so I have better understanding about fuel quality. Each car brand has its own engine design specification. Suzuki and toyota normally got good average through PSO and shell, honda cars normally gave good average on Total company petrol (normal pertol, not high octane). Try not to use city outside fuel pumps, always trust the pumps located near city mid.. this is all my personal experience.