Amsoil, getting harder to find. Next would be Mobile 1.
I use Amsoil and love it! I paid the $20 to become a preferred member after I did the math and figured out with Amsoil and the extended drain intervals it would save me around $300 in a year to run it in everything I've got. I was running Syn3 and the Amsoil lowered my temp around 10 degrees in my Harley.
I deal with a local guy and it costs me around $8 a quart. He delivers it to me or you can have it shipped to your door.
Amsoil. Three different grades in the three different holes. I just order it online, and it's here in 1 or 2 days. Not the cheapest, but it works for me.........