dude----get a grip on life-----go to Walmart a buy a jug of oil ----pick one any one----and change it once every ten years------really---- a big deal over oil---better yet buy a dyno test them all and report back here
oil technology has come a long way since the manual was printed you should expect to see extended life from a good multi visc oil like 10 w 30 you may want to add a zinc additive for flat tappet lifters or use a cc grade diesel oil
Now that you have the oil type figured out, you might consider anit-freeze. My preference for most of my cats is Prestone, but on an IMP make it Quaker State!