I have found that oil is personal thing! but it does help to have a decent oil pressure guage to check.

Use fully sinthetic there is no cheap alternative

I have a ZVH and I have used 0-5 good for power, ie oil drag is minimal but pressure drops a little low at idle.
15-40 mobil racing, good all round but maybe a little thick for the modern bottom end, but no complaints so far.

So my personal opinion is any sinth oil ranging from 10 to 60 !

Simon.