I just answered my own question in another post.
I just called my Harley dealer and as of my first 1000 miles service on my Road King Classic, the service manager told me that Harley recommends the use of the same Full synethic oil in all 3 holes.

 

Then I would find another service department. Motor Oil for motors, Gear Oil for Gear boxes. I wonder why HD sells Formula+?

 

If price is an issue go to your auto parts store and buy any GL5 rated 75w90 gear oil or higher. It will last 15,000 miles in a HD trans and will be more shear stable than any motor oil. One guy here was running a GL5 75w90 that he bought at a farm supply for $1.50/qt. Worked just fine. Shell Rotella gear oil at Walmart is a good choice as well.

 

He said that because he is toting the "company line". HD doesn't make a 75w90 gear oil so they will sell you what they sell.

 

Probably for the same reason that they also sell HD 360, a non synthetic oil. Different flavors for different tastes.

Many old-timers with the older bikes prefer a non synthetic.

 

Not true. That is what HD's Formula+ is.


FYI: HD no longer recommends 20w50 motor oil in the in the Gear box. The MoCo recommended HD oil in the tranny is Formula+ which is a Gear Oil and non synthetic.

 

I called three dealerships and they are all putting Syn3 in all three. I have Syn3 in all three now and am satisfied but think I will try Formula+ in the tranny and primary and see if I can tell any difference. I even switched to Syn3 in my Evo engine and was completely satisfied and think it worked especially well in the hot southwest.

Not saying Syn3 is better than any other synthetic oil but I think it is just as good. I am not **** about the minor differences in motor oil nor do I dislike Venezuela any more than I dislike Saudi Arabia. In fact, I like Venezuela better, especially the women.

 

The oil analysis on Bitog says Formula+ is a 50w oil with very weak additives. It is also about 2x the price of generic dino 75w90 gl5 gear oil. Please show me where HD has published a spec on Formula+. I would really like to see it.

 

Everyone should keep in mind that the SAE viscosity tables for motor oil and gear oil are not the same. A 75w90 gear oils is roughly the same viscosity as a 15w40 motor oil. Formula+ is roughly a GL-3 85w140 gear oil.

As for Harley not recommending a 20w50 motor oil for the tranny, that is not true when it comes to their Syn3. It clearly states on the bottle and in the catalog that it's recommended for use in the engine, primary, and transmission. And all the CVO bikes come from the factory with Syn3 in all three holes.

 

I went up to the Wheels Through Time museum today and one of the displays with vintage oil cans caught my eye. These two oil cans are identical, one is showing the front label while the other is showing the side. Note the "use in motor and transmission," indicating that Harley's recommending their Syn3 oil for both the engine and tranny is nothing new for them. I'd say these cans are from the 40s and they were clearly recommending the same oil for the engine and transmission way back then.