A standard grade chainsaw bar & chain oil is going to be about the same thickness as SAE 30 oil, but I would buy oil designed for chainsaws. It will flow better & stick to the bar/chain better.
A 30W bar & chain oil may flow out of the jug slowly during the winter months, but the chainsaw engine will warm it up quickly. Would 20W be better in the winter & 40W during the summer? Most likely, but I just buy the basic stuff.
My primary saw has a manual oil adjustment for the bar/chain oil. For that saw, it's basically a low, medium, and high setting. I typically just run that saw at the medium setting when using an 18" bar & .325 pitch chain.
My 82 year old dad gave me his larger 65cc chainsaw this past winter. (He still has two 50cc chainsaws, & we don't want him out there cutting by himself any more). His 65cc chainsaw states 1-4 complete turns for the manual oil adjustment, & you use your bar length to determine that. If I was running a 20" bar with a 3/8" pitch chain, I would probably turn it out about 2 turns. If I was running my 24" bar with a 3/8" pitch chain, I would turn it out a good 3+ turns. Bars longer than 24" & I would turn it out 4 turns.
If I am running a decent bar/chain oil, the gas tank will always go empty before the bar/chain oil reservoir. I always fill both at the same time. My guess is most professional grade chainsaws are going to some type of manual oil adjustment. The large old time chainsaws had a button to pump extra oil when needed, too.
An older style saw like the current Echo CS-680 would have those features -
Automatic, adjustable oiler with manual over-ride
Allows the ability to match cutting conditions for reduced oil consumption
Post #21 - just trying to do my part! Chainsaws aren't political at least!