Need 10wt but have 5 and 15wt – what ratio do i need to use?

I don't think it works quite like that…

I'm sure someone else will know better though

I'd just go buy the correct stuff personally 🙂

EDIT – Double post 😳

not for me 🙂

I'd mix the two 50 / 50

it is unlikely to be 10 w exactly but it will be near enough – assuming the two oils are compatable

I thought you could mix and dilute (not sure where from).

My thought would be equal measures of each to get to 10wt?

Let us know how you get on 🙂

Are they the same brand/type of 5 and 15wt? – some combinations don't mix well

When mixing oils — not a good idea to begin with — remember that one part 10 weight oil mixed with one part 20 weight oil does not make 15 weight. Rather, it's 13.3 weight

http://www.motorcycle.com/how-to/how-to-replace-fork-seals-3442.html

both rock oil

How crucial is it? Your forks have adjustment do they not?

if you want 10 w then buy some. If you are happy that its somewhere close to 10 w and that your adjusters will compensate than mix it

I had 5 and 15 with my old boxxers and would mix equal amounts to get around 10. Always worked fine for me.