In Reply to: Re: Oil tested after 10 years use. posted by Ultradog MN on December 11, 2018 at 05:53:50:
That is exactly what I am saying. Engine oil is a carefully engineered high performance man made material. Impurities introduced by operation inside an engine are a major concern and they can be be removed by filtration. Chemical depletion of the additives that are crucial elements of engine oil performance can be monitored by used oil analysis and added to extend service life - a practice employed by many large fleet owners. But the real nail in engine oil's coffin is the breakdown of the molecular structure of the hydrocarbon chains that comprise the base oil.
Remember - a base oil is produced from crude or synthetic feed stock by carefully controlled thermal, physical, and chemical processing which alters it's molecular structure and produces a finished lubricating oil with very carefully controlled physical properties. After blending with additives it is placed inside an operating engine that subjects it to additional thermal, physical, and chemical processing which further alters it's molecular structure. That results in different less desirable physical properties and degrades it's performance as a lubricant. The life cycle chemistry of lubricating oils has been exhaustively studied and documented. Here is a "light" read on the chemistry of base oil breakdown:
Engine Oil Breakdown
Most people are not going to wade through that article so here is a short quote summarizing one of the primary processes that kill engine oil.
Oil oxidation is no different than other commonly encountered oxidation reaction, such as rusting. Just like the effects rusting and other corrosive processes have on metal substrates, oil oxidations results in a catastrophic and permanent chemical change to the base oil molecules.
In the case of oil oxidation, the reaction results in the sequential addition of oxygen to the base oil molecules, to form a number of different chemicals species, including aldehydes, ketones, hydroperoxides and carboxylic acids (Figure 2).
So yes Virginia - your engine oil does in fact "wear out" and it happens relatively quickly. Hardly surprising since AFAIK every material in the universe wears in one way or another.