Does 2T have a placebo effect?

[macca]

Ive been running it for the last few hundred litres of fuel. Didnt notice any real fuel economy difference or engine smoothness. But my on my did it quieten the 12mm pump. It was really loud and ratchety sounding. A lot quieter with 2t oil.

I don't know what a 12mm pump is, are they normally noisy? Is it worn therefore makes more noise?
Does using an additive hide a problem, having something fail in the centre not knowing it was an issue is the reason for the question.
The other side of the coin is, a problem starts to appear then adding an additive could get you out of there.