the best oil is the one you change often
2. get an oil temp gauge and if you ever see 300f when riding your normal routine get and oil cooler or adapt one
3. the most recomended oil on this site is rotella 15-40 stuff, they also have a synthetic, but I use delo400 which is also a deisel recomended oil and the bike loves it...so does my truck. jajaja
15-40 is a good compromise for wieghts...cold climate go 10 40, really really hot like desert go 20-50...as per the manual...
if your temps never vary more than 15 degrees F. then you can actually run a straight grade oil which is the best.
in fact Im starting to use my oil from the xr in the truck to save some $$ as I change the oil in my bike every 600-800miles...