20- 40 oil?

[paul vangogh <levi443@xxxxxxxxx>]

                     For recently-bought R850R
   
  In my first real oil change, a bike mechanic has recommended some 20-40 oil.
  He pointed to a 55 gallon drum he has and mentioned  5$ per qt.
   
  Should I worry about the  20-50  rubric?
   
  thanks in advance
   
  -------- Paul,     reader of "The Perfect Vehicle: What It is About a Motorcycle,"  Melissa Pierson,  1998