Do I need to buy fork specific oil or is it just standard motor oil in a different bottle for example?

Its specific oil – but you can buy it by the litre from motorcycle shops which is a lot cheaper than cycle fork oils

dont mean to patronise but make sure you get the right weight. you can often find good quality stuff on ebay pretty cheap too.

Weight? I thought oils were measured in viscosity and temperature rating?

http://www.upmpg.com/tech_articles/motoroil_viscosity/index.html

Viscosity is also referred to as weight in oil is it not? Even tho "weight" is incorrect – the w = WINTER not weight

yeah by weight i meant viscosity. most fork manuals refer to oils by weight, eg rockshox 15wt, fox 7wt etc…

There's a chap on wiki called pvd I think who has a lovely list on his site (might be under the motorcycle section) that lists all the spec of the oils including the bicycle brands so you can scan down and see that expensive Rockshox oil is in fact inexpensive Torco oil etc!

half way down

how do you find an article by user on wikipedia?

Clicky Oily Linky

so for my rockshox it says i need 15wt oil for the lubeing and 5wt for damping. But is taht genuine 5 and 15wt or should it be 7wt and 20wt?

Just serviced my Reba's with Shell 15wt motorcycle fork oil after 25 hours use….fantastic. Smooth and loads less stiction. Not convinced factory had put enough oil in lowers and what came out was already dirty and contaminated with grease and swarf.

I've got half a bottle of 7.5wt fork oil that I no longer need, if anyone wants it (for the cost of postage).