To describe this quandry I'll propose a thought experiment; Bitog's Cat.
Imagine a cat in a box, with an opening at the top, and a stand with a screen around it to prevent the cat from knocking it mover. On the stand there a dish with a vial of poison in it. There is a metal ramp, angled slightly, to allow a ball bearing dropped thru the opening to hit the ramp and bounce towards the vial of poison. If the vial breaks the poison will kill the cat.
In one case imagine wiping a layer of a thin oil on the ramp, say Mobil 1 5w30, and filling the dish with the vial of poison with just enough oil to cover the vial with a thin layer of oil. Now drop a ball bearing thru the opening, which will hit the ramp and bounce towards the vial, hit the vial, and make a noise. Do the same with a thicker oil, say Delvac 1, and also add enough of the thicker oil to the dish to cover the vial a thicker, deeper layer of oil. Drop a ball bearing thru the opening.
Which oil will produce more noise ? Probably the thinner oil.
Which oil will produce more Fe in the oil on the ramp ? Probably the thinner oil.
If done repeatedly, which oil will produce more wear on the ramp ? Probably the thinner oil.
Which oil will more likely result in killing the cat ? Probably the thinner oil.
But, since we are in a superposition of states, that of increased noise, more Fe, and the belief of lower wear with thin Mobil 1 regardless of Fe and noise, we really don't know until we perform a measurement by opening the box, measuring the wear on the ramp, determining the Fe in the oil on the ramp, and seeing if the cat is dead :^)