What is a good replacement oil for Harley Davidson oil?

Answer 1

Lets start off by saying that Harley, or any other manufacturer does not make their own oil. I think Harley's oil is made by Sunoco others say it is very similar to Mobil 1.

Therefore, any good motoroil formulated for motorcycles is highly recommended. Harley recommend a 20w50 motorcycle oil. Do not use oils formulated for cars, not for airplanes, as a matter of fact in the Harley owner's manual they recommend to use DIESEL rated oils (C, C4, etc.) when you cannot find Harley oil WHY? , because diesel engines need to last hundreds of thousands even million miles before they are rebuilt.

Just make sure you use an oil with a very high VI (viscosity Index) number, i.e.:

The high and low temperature performance of oils are described by the Viscosity Index. The VI tells us how much the oil thins out as it gets hot. Oils with higher VIs maintain their viscosity better at high temperatures. If the VI is 90 to 100, we call it Group II; if it's refined to a VI of 110 to 115 we call it Group IIa. In the late '90s, an even more involved process was invented yielding base oils with VIs over 120. These base oils are called Group III or "unconventional base oils." The higher the VI, the fewer additives are necessary to achieve the required viscosity. For example fewer additives are needed to turn a Group III base oil into 10w-40 than are required for Group II base oils. Group III oils have essentially no paraffin and wax in them, at least as compared to the 12" dinner candle per gallon in Group I oils.

Valvolene or Mobil are as good as any.