Let me 'splain' the dif between regular oil{dyno poop} and syn. oil for people with a small brain like me. Dyno poop oil has molecules that are all different in size and shape. Syn. oil is 'man made' and has ALL MOLECULES the same shape and size , {less friction} . I pesonally like and run BEL=RAY EXS 10-50 wt. in motor and gear saver 80 wt. primary 85-140 wt. trans. Changed the oil in my lawn mover {push type} with 4hp. to BEL-RAY 10-50wt. EXS {SYN.} because didn't have dyno poop ,and WOW , pulled the rope and could not believe it. Ran 500 + rpm higher ! Shut it off and thought about it for awhile ,what did I change other than oil ? NOTHIN ! Pulled the rope again ,same thing. BUT , in my opion ,ANY OIL ,will get you alot of mile. PERIOD ! I and 3 freinds have put over 100,000+ miles on some EVO's with the 'old' H-D oil '360' and no major problems. I remember running the old H-D oil in the 70s and when you pulled your cap off ,it looked like you were washing dishes ,so much bubbles. We ran KENDALL in those years. good stuff , straight 70 wt. PHX.AZ.