I have a 2007 GMC 2500 HD Duramax diesel with the allison transmission. I will be pulling a FSW 32 Weekend Warrior. I have around 4,000 miles on it and was thinking about putting in Mobil 1 synthetic. Any input from you pros would be helpful. Also would you reccomend synthetic for the tranny? I live in southern California and would also like advice on what weight oil.