Your feel analysis is invalid,
Do proper wear analysis on it by tearing it down and measuring wear.
If you want feel rationale and somewhat factual stuff, i have seen an old ford 300 inline 6 engine used as a generator to run a welder, its oil was changed when some loose.change was found, meaning about 3 years or so. Only topped up with whatever crap was lying around.
Yes, it worked sweet. Its inefficient as mud but it feels perfect in running, and rebuilding costs abt same as a dozen pizzas.
Its not empirical evidence that the ford 300 can be run with no maintenance. It may sort of run but not top notch.
