So I have seen some posts on using gear oil, specifically Mobil 1 75W90, and it will either be awesome or destroy your stator. All of these posts are from around 2008-2010, so since the has there been confirmation that it's alright to use or will it really eat away at the brass and copper?

 

Better yet does anyone have real world experience with it? Like running thousands of miles with it?

 

there is no advantage to using gear lube type oils in a sporty trans,,,,75w90, gl4, gl5 and such. the gearset was not designed for it and the clutch friction plates are not specced for it. Spectro oil company has a very good synthetic Sportster Primary/Trans Lube. STL . Great stuff!! Other manufactures still makes XL primary oil, I am just not a fan of the HD formula Plus,,,,had issues with sticky plates.
m

 

Here is your answer on gear oils in the Sportster primary/transmission -

https://www.hdforums.com/forum/sport...-answered.html

Some Gear oils have additives that will effect copper (your stator) some do not.

HD Formula + is a GL1/GL3 rated GEAR oil.
Harley Davidson Formula+
Application: recommended for heavy-duty service in manual transmissions where the manufacturer normally recommends either engine oils or GL-1 lubricants.

http://www.bobistheoilguy.com/forums...ue#Post3087905
Harley Davidson FORMULA+ Trans and Primary Chaincase VOA
(Mini VOA via Amsoil)
Petroleum based.

Ca 169
P 230
B 210
S - some
Zn - essentially none
No other elemental additives.

Vis. within SAE 50 range.
Listed as a GL-1, does test out as a GL-3.

 

Spectro STL (Sportster Transmission Lube) is a 75w140 GL-1 product.

I use it in the primary of my big twin

Ken

 

Here is a link to my last 20,000 miles trans/primary Used oil Analysis-

10,000 miles on Red Line MT-90 manual transmission lube
10,000 miles with Red Line 75w-110 GL5 gear lube
I am running Red Line 75w-90 gear lube now.

https://www.hdforums.com/forum/oil-a...l#post16775722

 

the mobil one gear oil will work, i use it in my 01 sport, never an issue, not much diff from the hd oil. i use the heavier weight however since i find the lighter weight seems to effect shift, no issues in cold weather either. the varnish on the stator winding is not effected. as far a the clutch goes, it will not cause issues either, rear ends do have friction clutches also. where you would possibly get into trouble here is if if had friction modifiers in it which it does not.
oil is a HUGE DEBATE and NEVER will be settled, so use what you feel best with research.