does anyone use the clutch oil from the club?

It should be fine. The original Hudsonite was thin. To give you an idea, as an emergency substitute they recommended a 50-50 mix of 20 weight motor oil and kerosene. That's pretty thin.

my test has always been a "nose test". If you smell original Hudsonite it has an unusual odor + it is also dark in color. The main purpose of the Hudsonite is to keep the cork soft so they won't harden & crack.

I've found after installing a new clutch disc, after a few weeks, a good idea to drain the Hudsonite (& I always drain it into a measuring cup to see exactly how much came out) as some will have been absorbed by the new corks & refill it.

One of the 1st things I'd always do after purchasing a Hudson would be to drain the clutch & replace whatever was in it. Sometime literally nothing, sometimes way too much.

I can't remember how viscuous Hudsonite is as haven't "done" one in a few years but have a 1 gal. can of the original stuff I've been using for years + have some of the small cans Permatex made for the Club many years ago.