OK. Here is my two cents worth on fluids for the three major applications we have on our bikes (not including brake/hydraulic clutch fluid):
Engine: Amsoil SAE 20W-50 Synthetic Motorcycle Oil (MCV)
SE 6-spd: Spectro Heavy Duty Platinum 6-speed Transmission Oil
Primary: Spectro Heavy Duty Primary Chaincase Oil
References:
Amsoil:
AMSOIL - SAE 20W-50 Synthetic Motorcycle Oil (MCV)
http://www.amsoil.com/lit/g2156.pdf (white paper on MC engine oils)
Spectro:
Spectro Oils of America - Transmission Gear Oils
Spectro Oils of America - Transmission Gear Oils
Results to-date:
Engine oil: looks very good, but has darkened up to look about like pancake syrup - 1850 miles
Primary: not opened up yet - 1450 miles
SE 6-spd: still clean red color (about like Big Red! - beautiful) - 1450 miles
Subjective:
Engine "seems" to have quieted down particularly rockers/top end. Changed to the Amsoil about 1850 ago. Prior to that, ran Mob1 VTwin for total of about 8000 miles (oil changes at about 4k miles). Prior to that used HD standard oil for 13,100 (oil changes at about 3k miles).
Changed out the OEM 5-spd to SE 6-speed about 2500 miles ago. Transmission shifting has most significant change. Extremely quiet with very little little "feel" when shifting up or down. This change happened AFTER changing to the Spectro oil. Prior to that change, I ran about 650 miles on Mob1 VTwin, then about 400 miles on Royal Purple 75W140 heavy duty gear oil. On both of these fluids, I could hear and feel the "clunk" when shifting. Not now.
My bike is an '03 UC with 68,000 total miles. Only major mods at this point are SE air filter, SE slip-on mufflers, SE 6-spd, Jagg 10-row oil cooler and an M6 primary chain tensioner.
TQ