Mobil 1 15W 50.....Walmart has the 5 qt. jug for $22.88. Been using it for a long time. Better than most so-called "motorcycle oils".

 

Mystik JT8 15w50 semi syn diesel oil, made by Citgo actually fulfills Harley Davidsons mention of using diesel oil if their oil is not available and why I use it.
No motorcycle oils have the same commercial heavy duty rating as the JT8