Also watch ur acceleration pattern. Coz CVT Gears does not require full throttle, Always press approximately 3/4 Accelerator, when the car is moving at 40 km/hr then u can press full throttle after leaving once, to achieve speed like a turbo. When at start u press full accelerator, Vitz will slow down and will give knocking sound, so u should follow the advice and watch experience without mixing hi-Octane. Always use a good fuel quality when u fill up ur tank, Total Parco fuels are recommended in Pakistan. Cheers