I have a 1000 mile service coming up this weekend on my 2012 FLSTC. I have read all the oil polls on here as well as a lot of other great info and have decided to go with: Mobile 1 V-Twin 20-50 in Engine Harley Formula +1 in the Primary Before I go any further, I realize that Spectro and Redline are very popular in trannys on this site, however, it is not readily available in my area. So I have decided to go with Mobile 1 gear oil. So, the question is - Do I go with 75w90 or the 140 wieght? I live in Southern Alabama and the temperatures here are quite high in the summer (by the way it is 73 outside as I write this!) and I would tend to believe that the 140 would be better but wanted to get the opinion of the great minds on this site.