What is the benefit/downfall to run 20w-50 in three holes? I know the manual says you can run it in all 3 holes. I guess my real question is if the manual says its ok, why do some people not do it?

 

Interested as well, probably a one size fits all to make it fool proof, but not the best for each situation

 

I MO engine oil doesn't carry the high pressure lube package that the shearing action of loaded gears need. Baker transmission recommend 75 140 gear oil, I think they know a little about gear lube.

I put 75 140 M1 in mine and it smoothed out big time. I have no idea what the PO put in it but was probably dealer serviced.

 

Agreed on the shear properties of a gear lube vs a motor oil.

 

New owners manuals say SYN3 2nd choice. Formula + or their new synthetic which are both non-detergent gear oil in transmission and primary first choice. Motor oil is high detergent. Keeps crud in suspension so filter catches it. The transmission and primary do not have a filter. Just quoting what the oil engineers say at major brand websites.

Motor oil will let the clutch slip a fraction longer then gear oil does. Depending on your driving habits, could be a factor. (motor oil will fill a little smoother if you let clutch out slowly) However, if your clutch is adjusted correctly and you let it out, it will never wear out on a stock bike no matter what oil you have in there.

 

I would recommend you not use syn3 in your primary. Energy One Clutch told me that syn3 is too slippery and they had customers who experienced clutch slippage. Makes sense. I would use Formula + or a type F trans fluid in primary, and a gear oil in my trans. But this is me..... you will get 50 other "suggestions" on what to use. And yes, oils do make a difference in how your bike shifts and finding neutral.

 

With today's advanced oil formulations, you will get many, many miles of trouble free service following the manual's advice.... but the MoCo manual often injects marketing into their recommendations... it isn't always listing what is best for your bike. The MoCo only cares about two things- profit & getting you past warranty without a claim...

There are oils that are better formulated for the different needs of the three different applications (engine, primary, trans)..... many of us feel better using the proper lube for the proper application... The gains in performance and/or less wear may not be noticed by many or until well over the average miles driven by most HD riders, but I believe they are real, even if they are not extreme....

Will you hurt your bike using 20W50 in all three holes.... Nope!

Is 20W50 the best choice for all three holes... Not in my opinion...

 

I agree, you can use it in all 3 but there are better options. I use Amsoil but there are numerous other options.

 

I usually recommend Redline or Belray for my customers, each fluid has been optimized for it's application. I personally think the "one oil fits all" approach is a mediocre way to go about maintaining an expensive machine.

 

As others have said, you can use SYN 3 or any motorcycle 20W50 in all holes but they are a compromise oil. There are additives the engine likes but the clutch and transmission don't and vice versa. Syn 3 doesn't have the additives package that different oils have. It's a compromise where additives are left out or are a minimum so it works but not as good. To answer your question about why I don't use one, I use different oils that have the right additives for the application. Engine oil in the engine, gear lube in the transmission, and clutch friendly oil in the primary.