Energy conserving oils are labled as such (there is a circle with energy conseving written within) and are usually 10-30 or lighter. 10-40 and heavier are usually not so labled. The hang-up is moly that is added to the EC oil and that could let your clutch slip, in theory. Multipurpose oils accepted by the major diesel engine builders seem to be the way to go, such as Shell Rotella and Rotella synthetic or Mobile Delvac One or Cheveron Delo.
I think these bikes will always need close attention to valve clearance, but especially so when new. Poisen is dead on; if they wear in enough to get so tight that they do not chatter a bit, then you will get heat damage. Get an experienced friend to help you do the first valve adjustment.
In regard to using only 2.5 quarts of oil, DO NOT just go back and add the balance of the specified amount! Check the dip stick with bike level. If its not low, you did not get all the old oil out. There are two drain bungs under the 13000 engine -- you gotta remove both.
prs