So long as you have satisfied yourself you are correct that is the end of the matter no matter how wrong you happen to be.
As an aside, take a glass of water and add a teaspoon full of sand to it. Shaker it. Does viscosity change? No? I wonder why given you believe entrained matter changes viscosity. Incidentally viscosity and lubricity are two separate characteristics.
Combustion products in engine oil are entrained matter although some oxidation does occur which does not adversely affect lubricity or viscosity. What does get depleted in engine oil are additives which are the principal reason for oil change.
On the matter of combustion products, provided the diameter of the products do not exceed oil film thickness they will do no harm and will be removed by the filter. Combustion products in the oil of a well maintained gas engine are minimal as compared to a trunk piston diesel engine.