Double virgin olive oil (Italian) every 200 miles, whatever the heck that is!.
Seriously, if you change frequently any good dino oil will probably work fine. I like Mobil 1 for about 3-4,000 miles with a filter change every two times. This is all that I have used in my Triupmh triple and last two Guzzis. As has often been stated, it's not the oil it's the frequenncy of changes.