When I emailed Redline about the 20W60HD it took them about 10 days to get back with me. In that time period of waiting, I got impatient and ordered the 20W60HD, MTL, and Shockproof from
www.myoilshop.com .. I received the 20W60HD, then rec'd the email about using 20W50. I emailed Redline back and they said using 20W60HD would not hurt anything. The tech said he liked using 20W60HD in older noiser engines. The strange thing is that on Redline's website, it says nothing about older more clearance engines. It says for American air cooled Vtwin engines. Under 20W50 it says street driven cars/trucks and large clearance air cooled engines. I might try to send back the 20W50 and get 20W60HD. I thought the 20W60 may be better in the summer heat? What does the HD in 20w60HD stand for, heavy duty or Harley Davidson?