Engine Oil – My answer to the question?
Caltex/Chevron Delo 400. They have other Delos, (DELO, aka Diesel Engine Lubrication Oil) including Delo 400 LE which you do not want, just Delo 400. The last I got was $85 per 20l drum, but is about $35 at the servo for 5l.
Its 15/40 and was recommended to me for the Bergs by a guy who raced them and won in the States, and was also a petrochemist who was involved in its development with Chevron. Excellent credentials. Many use it in their Bergs as a result, once they overcome the obvious concerns, and don't go back.
In the only scientific test I could do, the valve gear was repaired in my 501 after a cam follower bearing failed at about the time they do, ie 150 hrs. My fault for letting it go too far. At the time I switched from Mobil 1 Racing 4T used up until then. A well regarded full synthetic bike specific oil. Now another 300 hrs and valve gear is still fine, along with the rest of the motor with original bottom end still, with Delo 400 exclusively. It goes in all the dirt bikes here, and my tractor, is semi synthetic and works great with wet clutches and rolling element bearing motors.
Perfect for the big trip, because its available pretty much anywhere.
Because you wanted to know