If I mix equal amounts of 5wt with 10wt do i get 7.5wt or is there more jiggery pokery to it than that?

In a nutshell, yes.

You should get 7.5wt as a result. Not sure what it’ll do to the damping though, I’ve run 10wt in Revelations and it left them feeling decidedly spiky and “dead”. I abandoned that experiment and have refilled with 5wt oil, now all is well.

Ok ta, might give it a try since i have the 5 and 10 at home already.

Im pretty sure its not as simple as that.
Have a search for peter verdone, there’s some more detailed stuff on fork oils etc on there.

I’m pretty sure it doesn’t work like that either. I’m also pretty sure there have been arguments/discussions about this before.

Oil Mixtures Calulator might help.

fork ‘andles?

(sorry)