What weight of fork oil should i use?

[Forde]

Thought id post this up as a lot of ppl on here know a lot more about suspension than i do.  I want to stiffen up my forks a bit as they have always seemed very soft to me although the fork seals sucked so that could have been a factor...  Im thinking of using 15wt fork oil, i think the standard is 10?

i weigh just over 160 kilos or 9.5 stone if thats any use.

Cheers

[gsxr400 racer]

id ask brian , i always like 10mm more fluid my self than what stock says