the slippery kind.... lots of good results with rotella i run 15-40 dino in the sumo and dirtbikes and the Synthetic in the street bikes allways good results and ability to get it everywhere including wal-mart for when you need it down the road on a trip.
Check the ratings in your manual and compare them to the ratings on the bottle. The major difference between car oils and motorcycle oils are the detergents and the enhancers, hence why you need a good motorcycle oil.
People say im overboard but I change my rotella every 400 miles since its only 11 bucks per gallon. Repsol makes a very good product however its to rich for my blood.
Another +1 to Rotella T6. And a +1 to what Erik said about no oil really being bad.
I ran Rotella in my sportbike, but since from what I've heard, the DRZ likes to shear oil down quickly, I've gone with a more quality oil -- Amsoil. Shear resistance is far better than that of Rotella.