I'm going synthetic and I'm going to use Mobil 1. My questions are these:

1. 15w-50 or 20w-50; why one over the other??
2. what weights in the primary and trans?
3. This will lower the operating temp and quiet the motor down...right??

Thanks!! I'm sure this has all been covered, but I couldn't find these specific answers anywhere.

 

Mobile 1 V-Twin 20-50 in the crank case
Mobile 1 75w-90 gear lube in the tranny.
HD Primary lube in the primary.

 

Above answer is correct, but you can use Mobil 1 20W-50 in your primary as well. It works just as well and saves having to keep another lubricating oil. I had usedeither Amsoil or Mobil 1 in my primary then tried a change of HD Formula Plus. I didn't see any improvement so I switched back to Mobil 1 or Amsoil. Using Mobil 1 or Amsoil just depends on what Ican conveniently find when it comes oil change time.

I noticed a significant difference in my bike when I changed to fully synthetic.

 

Same as him except regular Mobile1 15w50 in the crank.

Edited to add, saw close to a 20degree drop in operating temps with the Mobile1. Running around 250 with dino...around 230 with syn.

 

I am running amsoil 20w50 in the engine and primary & amsoil severe gear 75w90 in the tranny.
Bike runs from 190 to 230 depending on the temp outside and riding conditions. Average temp is 200 - 220. I've got about 2000 miles in since the change and have no complaints.

Why 20w50, b/c the manual says so I guess.
Why 75w90, I just figure a gear oil is better suited for the tranny than a normal 20w50.The oils are the same weight, just have different additives.

 

I run Mobil 1 20-50w in all three spots. It really quieted the motor, ran cooler and the trans shifts much better. I had a problem finding neutral with regular H-D oil before changing to M-1 - now I find it everytime.

Ordered from an online source and saved some $$$. I run M-1 in all my cars and my lawnmower. Have for years with great results. J

 

Make sure you get the Mobil 1 for V-Twins and not the regular stuff. Its got different additives in it specifically for the aluminum air cooled V-Twin motors that the regular automotive version lacks.

 

thanks, now I just need to find out where to get the stuff...

 

Try Auto Zone, If they don't have it in stock its an orderable item for them.
Most other places can't, which annoys me because my son works for one of their competetors, but he can't get it for me so I can't get it for his discount.

 

O'Reilys carries it in the back of the store, not on the shelf.