No, it won't do any good, don't waste your money.
Instead, diagnose the issue properly, then decide what can be done.
As engines wear, they can produce a knocking noise when cold, due to the piston moving in the bore, called 'piston slap'. If this is what you can hear, it should disappear after a few minutes, and can be ignored.
If the knocking is always there, we need to determine what is causing it. Usually a knock suggests bigger clearances than meant to be. No oil will fill the gap. You have cleaned the spray bar, suggesting you thought there was a need. If it was necessary, any damage due to insufficient oil will not go away unless worn components are replaced. But that may not be necessary, so don't panic yet.
Lack of oil at the top end may have caused worn cam lobes. If the face hardening has gone, it will need replacing as wear will be rapid even with the best oil. But if not gone through, keeping oil in may mean just living with the noise.
Have you checked the valve clearances? Would be a good place to start. Then report back. Plus any comments on the above.
I'm assuming a petrol engine. More details would be good. 1.2, 1.4, 8v, 16v, etc.
