10w30
HD makes a weight of oil they call "Sport-Trans" that is made for use in the Sportster primary. Or, you can use any 30W non-detergent oil.
Mobil 1 is a name brand, what you need to know is the viscosity. Make sure your oil says 20w50 on the bottle. That is what most people use in their Harley.
20/50
20/50
The viscosity preferred by many people is 10 W, but you can also use 5 W or 15 W, according to how stiff you want the front shocks to be.
3 U.S. quarts
Cannabis oil viscosity refers to how thick or thin the oil is. The viscosity can affect how easily the oil can be vaporized or absorbed by the body. Lower viscosity oils tend to be thinner and may be more suitable for vaping, while higher viscosity oils may be preferred for topical or oral use.
SAE 20W-50 Synthetic Motorcycle Oil
Of course you can but when you do you are changing the viscosity of the oil. Your engine requires a certain weight or viscosity of oil. Use only the weight oil recommended by the manufacture.
5w30
I understand you can use the same oil viscosity in both motor & transmission on the 2008 harley roadking!