Well, here are the results of running Castrol for two seasons of firewood cutting. No noticable wear, cylinder crosshatch and piston machine marks still like new.
Quite low deposits in the exhaust port and muffler, next to nothing for varnish deposits around the rings or on the piston.
The oil seems to prefer running hot, there's nothing to speak of on the baffle for deposits, in fact you can still see the braze color in the corners of the baffle. The clean streak in the exhaust port is where I ran a finger, it dumped a bit of soot just recently from idling while I was running it to get some fresh gas in the carb after having it sit for 3 months.
Bit of a different story on top of the piston though, a thin even layer of black carbon deposit, you can still see the arrow on the piston pointing to the front. So it seems this oil is fine as far as wear goes, but I would like to see a bit less buildup on the top of the piston. This ms250 has seen a lot of heavy use in dry ash, so no lightweight limbing duties for it.
Overall OK oil if you run your equipment hot enough to prevent buildup, the price is reasonable too.
Will probably try Opti 2 next season, my uncle's been using it in his 024 AV super, cuts enough wood to heat his house all winter and the saw is still running strong after 30 years of use.