He asked about the primary not the transmission.

 

Engine Oil requires a very specific viscosity, detergents, and non foaming additives. The clutch requires friction (or Non Friction) or similar additives. Motorcycles with separate transmission cases need only "gear lube" to lube the gears. Gear lube has a tendency to "stick" to components and not fly off from motion or reciprocating inertias. Transmissions are known to run better with 75-90 w gear lube or better. You wouldn't put gear lube in your engine, would you? Bikes with a primary chain case need only to keep wet (Oily) the chain, sprockets, and clutch plates. They don't need such specific viscosities, anti foaming agents, and detergents. Why not buy what each part of your motorcycle will do best with? I know you can run the same multi purpose Oil in all holes, but since the duties of each component are so different, I would only do it in a pinch if I had to. Since I don't have to, I buy different Oils. On the road if you wanted to carry just one bottle of Oil, I could understand that. You will rarely have to top off your transmission, or primary Oil, so I carry engine Oil. If I should need to add to the trans, or primary, I change my fluids when the trip is over, and get back to the specific fluids we just spoke about. Others on this forum will know well which fluids work "best" with Sportsters. I would learn from them, or bone up on the MOCO recommendations until then. Just as Important, don't "cheap out" just to save two bucks, on any dime store or auto parts store Oil, or Oil filters. There "IS" and "ARE" differences. Personally, if I was looking at a used motorcycle, and the owner went on about how he saves 2 dollars on his "Internet specials, or Auto parts store oil filters over the years, I would steer clear. But that's another thread altogether. I wont recommend one brand or type over another. Your bike, your choice.
This "One for All" school of thought comes from the Olde Panhead, Shovelhead days and maybe a little earlier when you could use straight 50 weight (petroleum) Oil in all three holes. With the advancement in Oils (synthetics) and Lubes today, there is a myriad of "better" choices to suit your specific needs best.

 

To the OP, your choice of a motorcycle specific 20-50 is fine. Just don't use a super slick oil like the Valvoline VR1 Racing blue sapphire stuff.
Ask me how I know this.

 

StevieC----use hd sport trans fluid (formula 1) in your primary which uses the same shared oil as the tranny made by harley or for harley

 

Just to follow up, I changed the engine with the Mobile One Synthetic V Twin oil and did the primary with Harley's Formula One. The Harley oil was even less expensive.
Next time I'll buy their Synthetic motor oil as well.
Thanks for all the help and the replies brothers!

 

i use mobile 1 in my engine, but would NEVER put an oil designed for all 3 holes.

 

I tend to agree, think it's kind of a cop out...thinking of going a different route for wife's CVO..then again I consider they have been using SYN3 in CVOs for about 15 years and would have kicked that product to the curb if they had information over such a long time that determined it wasn't up to the task

 

I'm sure you guys know that harley doesn't make any oil. While we're on oil, 95% of motorcycles on the road don't have oil filters and engine and transmission are in one case with one oil. There are bikes with over 200hp and some turning 12-13000rpm. So, I think using amsoil 20-50 in engine and primary and transmission would be fine. It has additives for shear on gears. Everyone can just put in what they like and be happy, because it ain't gonna make any difference anyway. There probably isn't one in 10,000 people that put on over 50,000 miles on a sportster. I bought this 1200T a few months ago. This is my 36th motorcycle and my 5th harley. OK, thats my two cents worth.

 

Hmmm don't be so sure, my sportster has over 51k miles. Cacomly and cHarley also have high mileage on theirs.

 

my 2005 sportster has 60,000 miles on it and still purring at 70 mph