For an air cooled engine, you'll want to use a thicker weight oil for the added protection.

10w30 is too thin, our piston clearances are too large and our required film pressures on our cam lobes are way too high to use this oil at the current wimpy car additive specifications.

20w50 is so thick it doesn't conduct heat way from the head as well as thinner oils do.   It is slow to pick the heat up, and slow to dump it out the casings in the sump area.   It runs the engine 15-20 degrees hotter than a 40 weight oil would do.

The 10w40 class of oils is the best "thermal conductive" fit for our bike's engine, and the Savage curiously was designed around 10w40 oils in all of its early testing.

Because we cannot get oil additive levels like what the bike was designed for any more due to API rules changing, we substitute the nearest available "economically affordable" oils, which are the Xw40 HDEO oils that are used in diesel engines and have much closer amounts of ZDDP to what we need.    We still have to bump, but not as much Redline is needed as if we had started from a car oil.

Do you remember 20w40 motor oil?    You do if you had an older Yamaha, as they were designed to use that somewhat stranger weight of oil.   They too use Rotella now as it is the closest fit for weight and required additives that exists currently.

https://bobistheoilguy.com/forums/ubbthreads.php/topics/4359102/The_new_Rotella_
T5_and_T6_no_l#Post4359102

Here is an 8 page thread of pure angry confusion over what API and EPA has just done to America.  

New News .... The new Trump assigned head of EPA has just requested 24 hour security personnel be assigned to protect his body because he is getting ready to clean house over in the EPA.



We want the first bottle or the last bottle, and NONE of the other bottles .....