first, find out the reason it is knocking.

1. pa-check mo muna ignition timing mo.
2. is there a knock sensor? it is possible the knock sensor has malfunctioned.
3. is the engine clean, no high carbon deposits inside the cylinders, spark plugs clean and in good condition? are there any issues that may cause pre-ignition?

imho, if there is a problem with the engine then changing the octane rating of your fuel will not solve your problem. go to the cause.