Doug Miller wrote:
....
The suspended solids in used engine oil are, for the most part, fine particles
of metal. The junk that collects on the bar during use is wood dust. Surely
you don't imagine that the two produce the same degree of wear on the chain
and bar.

A lot of the chips and dust are wood, but a lot isn't--the inevitable
dirt and other grime is at least as abrasive as the much smaller
diameter particles that made it through the engine oil filter...after
all, you wouldn't be particularly concerned to run your auto another 500
or even 1000 miles above the 3000 mi mark if you were on a trip and
needed that to get home for a more convenient oil change, would you?
The lube requirements of any modern engine are far more onerous...