In most engines the oil pump is driven by a gear attached to the crankshaft.
This is no always a direct drive, sometimes on older engines, the pump was driven by the camshaft gears or even the idler gear.
When detonation occurs, the fuel charge ignites quickly in an uncontrolled explosion, causing a pounding or hammering force on the piston rather than a steady push.
Moderate to severe detonation could be noticed as engine roughness, vibration or loss of power and eventually engine damage.
The main cause for the change in engine oil viscosity is