In reply to Bulls Crack:
M74 -> M73 for Stirling/Perth then onto M80 to Stirling. Take turn off for A84 Crianlarach -> Calendar, -> Crianlarach -> Tyndrum -> Take A85 to Oban. Appox 2.5 hours form M74. We use this route all the time visiting family in Coatbridge. We stay in Oban.
Alternativly, Loch Lomond then either Inveraray A83->Dalmally -> Oban(better road) or Crianlarach A82-> Oban ( 5miles shorter, but twistier)
Times are all about the same depending on time of day and volume of traffic through Glasgow. If going Loch lomond take new M74 extension to bypass Glasgow centre.
Gordon