niczumbo said it best. I used to use Mobile 1 in my truck and switched to Royal Purple. I use Amsoil in my bike. Any synthetic w/ a good name, just don't mix without flushing.

 

I'm perfectly happy with Harley's Syn3. I can fill all 3 holes in one shot, no problem. And when my dealer has their 25% off sale, it's a great price too.

 

Royal Purple is junk. Do a google search on scar tests and you will find out that RP barely beats out dino oil, and I mean barely. I've used mobil 1 and Amsoil, prefer Amsoil. I had a compression test done on a Road King that I had about 50K miles on it. After break-in, I only used Mobil 1 or Amsoil, the compression was almost like new.

www.bigmikespinstriping.com

 

So, which oil is best for primary and tranny? Like Warrior im running HD syn3.

 

They (Dealers) quite putting syn3 in tranny's last yr and I understood that was even harley idea...