No, but find out the requirements for the motor. Most normal motor oils don't meet manufactures requirements for wear protection.
You can use the same oil that you use in your motor
Use HD oil only and if you can afford use synthetic
Harley Davidson recommends it (Citco I think) but No!!! Just use the correct weight for your motor, time of year and how you ride it!
I understand you can use the same oil viscosity in both motor & transmission on the 2008 harley roadking!
no...but you can use screaming eagle synthetic oil in both the motor and the transmission which is supposed to be better anyways
Black
20w50
20w50 oil in the motor
20/50 motor oil and you can use sport trans fluid in trani if you can find it. this is the old fluid used, but you can also use the new stuff which is Formula+ or the synthetic Syn3 in the trani, both of which are available at Harley dealers.
I am not sure of viscosity, but if you have Harley Davidson on your fuel tank, you should use Harley Davidson lubricants. H. D. primary and trans lube or H.D. 20/50 synthetic motor oil will work just fine.
Harley recommends their own Syn3 synthetic oil or their regular H-D brand 25W50 fossil oil (both made by Citgo), but I use & recommend Mobil One 15W50.
"Best" is a very subjective term when it comes to motor oil, but if you use Mobil One 15W50 and change it every 5,000 miles (along with the oil filter) you will never, ever have any oil-related problems.