At the risk of beating a dead horse with the 20/50 vs 15/50.  Wouldn't the nature of your riding and the ambient temperature contribute as to whether either would be okay?  If you ride daily in a hot temperature or if you ride 2-3 times a month just bar hopping or going to the dealer for a tshirt, will that make a difference in the debate.  I have heard people use the 15/50 with no issues but I am still some what hesitant to do so.  I do like the price of the 15/50.  What do you think?