I use the HD syn and they change it every 5K miles. Still under warrenty so I just let them do the inspection and oil change at the same time.

 

+1 on the "bunch of threads comment"

HD Bulletin 849 (from 2005) regarding the use of SYN3 stated:
service intervals for SYN3 lubricant in primary chaincase and transmission applications.
:

Action Required
Please inform all dealership personnel that the extended service intervals for SYN3 have been approved
through the Harley-Davidson Motor Company are as follows:

All Big Twin:

Crankcase: Replace after first 1,000 break-in, then every 5,000 thereafter (unchanged)

Primary: Replace after first 1,000 break-in,

then every 10,000 thereafter or prior to winter or extended storage periods

Transmission: Replace after first 1,000 break-in, then every 20,000 thereafter or prior to winter or extended storage periods

All Middleweight (Pre-Evolution XL, Evolution XL and all Buell Powertrains):

Crankcase: Replace after first 1,000 break-in, then every 5,000 thereafter (unchanged)

(Please note that 1985 and earlier XL models require a crankcase service interval at 2500 miles (unchanged).)

Primary/Transmission: Replace after first 1,000 break-in,

then every 10,000 thereafter or prior to winter or extended storage periods

 

I've been running Amsoil 20W-50 in engine,and primary,plus Amsoil severe gear in tyranny.Personally run 10,000 miles on engine oil,but before I did that had it backed up with oil analysis.Came back fine at 10,000 miles,plus live in Louisiana.this is from Amsoil's web site:Recommended for use up to twice the motorcycle manufacturer change interval (miles/hours) or one year, whichever comes first, in engines, transmissions and primary chaincases. For Big Twin Harley-Davidson transmissions only, follow the Harley-Davidson recommended drain interval for synthetic oil of up to 20,000 miles or one year, whichever comes first. When using an engine filter other than AMSOIL Ea, change the filter at standard intervals.

For off-road use, change AMSOIL MCV at motorcycle manufacturer intervals.

Racing or modified engines are excluded from extended drain interval recommendations. Oil changes are at the owner’s discretion.

TYPICAL TECHNICAL PROPERTIES

SAE 20W-50 Synthetic Motorcycle Oil (MCV)

Kinematic Viscosity @ 100°C, cSt (ASTM D-445)
20.1

Kinematic Viscosity @ 40°C, cSt (ASTM D-445)
152.0

Viscosity Index (ASTM D-2270)
153

Pour Point °C (°F) (ASTM D-97)
-39 (-38)
Flash Point °C (°F) (ASTM D-92) 240 (464)
High Temperature/High Shear Viscosity @ 150°C , 1.0 x 106 s-1 (ASTM D 4683), cP 6.02
Four Ball Wear Test (ASTM D-4172 @ 40 kgf, 150°C, 1800 rpm, 1 hour), Scar in mm 0.40
FZG (ASTM D-5182), Load Stage Pass (Wear in mm) 13 (0mm)

Noack Volatility, % weight loss (g/100g) (ASTM D-5800)
3.90
Foam (ASTM D-892, Sequence I, II & III) 0/0/0
Shear Stability Kurt Orbahn (ASTM D-6278), % viscosity change 120 cycles 0.25
Rust Test - Humidity Cabinet (ASTM D-1748) No Rust, Pass

Total Base Number
11.1

PRODUCT LOOKUP GUIDES

* Auto and Light Trucks
* PowerSports Lookup
* Small Engine Lookup
* TRICO Heavy Duty

FILTER LOOKUP GUIDES

* Vintage Vehicle
* Heavy Duty Lookup

OIL COMPARISONS

* Motorcycle Oil
* Gear Lube
* Motor Oil

CROSS REFERENCE GUIDES

* Compressor Oil
* Master Filter Cross
* NGK Plugs and Wires

INSTALLATION INFO

* By-Pass Filters
* WIX Cabin Air Filters
* MANN Cabin Air Filters

MISCELLANEOUS

* Gear Lube Chart
* Two-Cycle Chart
* MSDS

 

IF you look at your owners manual it will tell you exactly what HD recommends for the change intervals. You know opinions on this is kinda like them butt holes, everybody's got one.

 

Hey, great info. Thanks a lot! Sure are a lot of guys running Amsoil. Back in my Corvette days a lot guys ran Amsoil. I always had great luck with Mobil 1, I guess I went with HD Synthetic because it came from the MoCo!?!

 

Yea, but the MoCo gets it from this guy...




There are better oils out there that are 100% syn.

 

96 EVO Ultra - 12k on HD crate motor

Engine - Mobil 1 20/50 or 15/50 (depends upon if 20/50 is available)- 5K during riding season maybe less than 5k if it is particurally warmer than normal. Always before an extended trip of over 1000 if more than 2500 on current oil. Always at winter storage regardless of mileage. I have pulled 20/50 M1 out of the crankcase at 3k and it still looked and felt like new. This stuff is too expensive to change before its time. Just paid $9.99 qt at Autozone for the 20/50 yesterday, didn't even have the 15/50 in stock. Walmart was out also.
Trans - Mobil Syn 90/140 - Once a season at storage in winter
Primary - Mobil Syn ATF - Once a season at storage in winter.