Be careful of oil grades. One man’s 5W is another’s 10W
Definitely! The closest I’ve found for RS (e.g. your rebas) for the lowers use Castrol Synthetic Fork Oil (10wt) @ 42 rSt vs 42.8 RS 15 wt, and for the dampers Castrol Fork Oil (10wt) @ 15 rSt vs 16.1 RS 5 wt. If you want to be exact use 1 part synth and 11 parts non-synth.
No idea why the two Castrol 10wt’s are so different 🙂
The 15 hours fox mention means you just clean / lube (fork oil) / cycle the forks / clean. You can mix fox / RS lubes and I use general grease on the seals with float fluid on the stanchions then wipe off excess when done. I’ve used all sorts of random oils and its been fine.
It sounds difficult but don’t worry about it. The lowers oil is just for lubrication. You need to be a little bit more careful with the damper oil (volume is IMO more important then viscosity) but the worst that’ll happen is they won’t compress quite as well, so you’ll have to take the forks apart and add more thinner oil.
Go to a local motorbike shop (and ask if stuck), you’ll pick up both oils for around a tenner.