Knocks in the engine appearing by increased revolutions and during car acceleration are the result of detonation.
One of the sources of detonation can be premature ignition when the fuel mixture ignites too early, and the released energy is only spent on increased friction in the connecting rod mechanism, which may result in damage of friction pairs, for instance, formation of tears on the crankshaft and bushings. This needs to be adjusted at a service station.
Another source of detonation is usage of fuel with lower octane/cetane rating than provided by technical requirements of the engine manufacturer.
Detonation symptoms are difficult start, black smoke appearing from the exhaust pipe and decrease of engine power. In this case such additives which increase the octane/cetane rating can be helpful.