I've pulled and drained the oil in my rear shock but the oil got tip over in my shed and I have no clue as to how much goes back in ? What would be the best type of oil to use ?? Questions I should asked before I pulled the shock but I got caught up in the "Why I am here I will do ................................" mode.
There's nothing mentioned in the factory service manual about the oil volume in the rear shock, but through some searches I did I found out it's should be around 9.5 ozs. I will be checking out the rear shock and suspension shortly on the C10, and although it shows no signs of leaking it will be interesting to see how much oil drains out, but I'm sure someone on the forum who knows more about it than what I've found will chime in.
I also found that the weight range was from 5w to 10w, and as far as what brand oil to use, I have been using Bel-Rey on my bikes for many years which is very good suspension oil. I don't know what weight oil is in the shock from the factory, and unless I hear anything different I'll probably go with 10w to start.
A good tip to make sure that you get the old oil out of not only forks or shocks if your not doing a complete teardown is to place them out in the sun for a couple of hours to warm up the oil so that it drains out more easily.
Like every bike I have ever owned I have always at some after riding them for awhile modified the forks and replaced the rear shock(s) and I'm already going to be installing new straight wound fork springs to start with on the forks along with a complete tear down and rebuild and go from there as well as changing the shock oil, but at some point I will most likely replace the rear shock with an after market unit.