Suzuki Club UK

As said whatever oil it runs well on. Temperature and carb/piston wear will make a difference.
But the recommended oil is
http://sucarb.co.uk/technical-carburett ... hamber-oil
like Scottie says

Tesco's Virgin Olive Oil, tastes better...

I had a talk to a chap the other day, as I was trying to track down some sae20. we looked up the oil viscosity charts, and found that 76 weight hydraulic oil is very close to sae20, and is quite easy to get your hands on too