Can I use the same oil ( Amsoil, Royal Purple ) or whatever I want in all three holes.

 

I use syn3 in all three..

 

You should check with each manufacturer.
I use Amsoil 20W50 v-twin synthetic in all 3 holes with very good results, it is recommended for all 3.

When I had my RG, I used Mobil 1 V-twin in engine, Redline MTL in primary, and Redline Shockproof Heavy in tranny, this combo worked very well also.

I am using the Amsoil in all 3 right now just for the convienence of having 1 oil on hand.

 

Use a 75w90 or heavier gear oil in your trans. The motor oils shear very quickly in there.

 

While some 20-50 synthetics may be adequate for all three holes, is that the best route to go simply for convience? Use what you will, even Harley sells Formula+ for tranny and primary as an alternative to Syn3 in all 3. I have found that a good GL5 rated tranny oil in my 6-speeds makes an astounding difference in shifting gears over Harley's Formula+. I would never use engine oil in my tranny. Formula+ seems to work fine in the primary, I suppose engine oil would be fine here too, as long as it doesn't adversely affect the clutch disks. In this age of highly speciallized oil products we have choices we never had before. Really superior products are available to us and I choose to use what's best rather than what Harley "conveniently" sells. A lot of Harley Dealers are starting to sell Red Line Shockproof gear oil, Bel Ray Gear Saver Hypoid Gear Oil, and Amsoil products.

Syn 3 in all 3, not me!