I'm a big fan of Mobil 1 V-Twin 20w-50 synthetic with a stock filter.
Sugar Bear don't want to look real dumb here, but what are you sayin about the final drive splines?All good answers so far. I would like to add just a couple things. When you do choose the brand you will run, stick with it. And make sure it is an oil with the needed "wet clutch" additives your bike needs. And unless you know the history of the 1st 17,000 miles of your bike, don't stop with the oil change! There are other very important things to check, change and adjust! Whatever you do, don't overlook the final drive splines! That could lead to a $700 or more oops!