Zinc oil additives

Dartnut said

I find it impossible to believe that the additives would just sit in the bottom of the pan.
The sump is supposed to sit on the bottom of the pan and suck out all of the oil mixture and send it through the oil galleries of the engine and then it drains back to the pan and is always recycled and the additives are in suspension.
Now a different argument to make would be that the detergents wash the Zinc additives off the cam almost right away, so they have little to no affect in preserving the cam and lifters, which is more believable to me...

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Additives in oil should not sit on the bottom of the pan. There is a terrific amount of turbulence in there. Now how well it mixes is debatable. Detergent and dispersant additives help keep byproducts of combustion in suspension so the oil filter can trap them. Poorly maintained engines show up easily on teardown with sludge coating everything not in contact with another part. Older engines like from the 50's that used nondetergent oils generally have a coating of sludge 1/4" to 1/2" thick on the heads under the valve covers, in the lifter valley and inside the crankcase.