I think the manual says any good quality fully synthetic 10/40. However, your bike has a wet clutch and they are likely to slip if you use a modern car oil as they have friction modifiers in them. Therefore it's probably sensible to use a motorcycle specific oil. Halfords fully synth bike oil should be fine. If you feel the need to spend more, try Opie Oils online for something like Motul 7100. They will supply a filter as well.
