I recently purchased a Yamaha 950 cruiser. I changed the oil the first time after only 30 miles following a prescribed (non-Yamaha) break-in technique to get rid of any metal. I continued with the Yamalube 20W-50 oil until the 600 mile check. At that time I switched to Yamalube synthetic 15W-50 which my mechanic said would be fine. A friend of mine who has been riding for many years said it was more common to wait until the engine had several thousand miles on it before going synthetic. Any thoughts on this?