Is it a piston style damper or a gear wheel?
On the gear wheels I use silicon oil which you can get in different weights. I have used 100,000 cst the higher the number the thicker. It does also depend on the strength of the spring. You could
Also buy a thinner oil maybe 10,000 then you can mix them to get the right level
Of damping. If it’s a piston type then you just need a thin silicon oil to lubricate, you just need to make sure the piston is making a good deal and not damaged.