What is the best synthetic oil to put in the primary?Currently, Mobil 1V 20 50 in engineMobil 1 gear oil in trans, HD dino oil in primary.

 

Personally, I would stay with HD Formula +.

 

what he said.

 

What they both said

 

I use Mobil 1 synthetic auto trans fluid in my '04 RK custom. No issues.

 

I'm using Amsoil 20W/50 in the Engine & Primary and Amsoil Gear in the Trans. I did a lot of research and it seems like a good combination.

 

What AtkRWC said. I think Mobil 1 is fine tho.
I do believe that using a sythetic gear oil is a good idea.
Both my bikes shift noticeably better. I had a tough time finding
nuetral in the 07. Switched to Amsoil 75-90 and there was an
immediate improvement.

 

called amsoil several years back and they said go lighter in primary(10/40). read somewhare fossil good for primary. have noticed very very faint seapage on my sprtsr but its just a back up bike low miles just sites

 

Amsoil states that they use no friction modifiers in their products so they are fine for the primary.I have heard some say to use Dino in the primary but haven'theard of anyone complaining about Amsoil causing issues. Not sure about the 10W/40, they seem to recommend 20w/50 now. All in all, each rider needs to do their own research and go with what they are comfortable with using.

 

All of the above.