I don't like K2 due to the excessive smoke when cold. I often need to start up a cold saw in the garage, otherwise I might not care so much. On another note, I just stopped by the local motorcycle shop and picked up a bottle of Yamalube and Super-M. I then ordered a bottle of Motul 710 off eBay.I'm sure some of the caster oils will have advantages in the most extreme conditions, but that's not really going to happen in as saw.
R50
Motul 800
Silkolene pro 2 sx
K2
H1R is fine, I just didn't care for the tuning oddities, and it's one of the most expensive oils out there.
Out of the thinner oils
Yamalube
Motul 710
Stihl ultra
Never ran any Lucas, I'm sure it's decent oil, but I can't get over how watery thin it is.