Hey guys, I recently bought a '06 Toyota Vitz 1.0L (new shape), freshly arrived from Japan with very low miles done.
In the first few days I noticed some sound of knocking/pinging at low speed driving. At that time I was filling it with Regular/Super petrol. Then I experimented with a full tank of Hi-Octane (HOBC) and sure enough the knocking went away!
To confirm this occurence I consulted some expert auto technicians and they all said that the knocking happens due to the fact that our regular petrol has a much lower octane rating as compared to Japanese regular petrol, which these cars are intended to consume. So our regular fuel (that has a comparitively poor octane rating) causes the knocking. Hi-octane solves the problem.
Knocking is extremely bad for the engine in the long run as it slowly damages the rings, pistons and other critical engine components.
Now I have started mixing the Regular petrol with HOBC in a ratio of 40:60 (40% Regular / 60% HOBC), and there is no knocking at any speed or any RPM. The fuel economy has improved and the acceleration is better. Also, it is obviously cheaper on the pocket to mix both fuels rather than just using pure HOBC.
Hope this tip proves helpful to any Vitz users who are experiencing the knocking problem.