Rohloff hubs in winter

Over the last few weeks, I've been pondering Rohloff hub efficiency in the winter.  For winter riding, the utility is unmatchable - the dual cable actuation means wimpy springs and frozen grease aren't obstacles to shifting (I had a few problems last year as linked below, but I'm thinking now I may have had moisture in my cables freeze as it was slushy for a while right before it cooled off), and my custom blend of oil has kept the hub in service and seems to have prevented freezing.  Rohloff ships the hubs with quite a light oil, almost whiskey like in it's consistency.  I had experienced it freezing last year, in fact their web site only recommends it down to I think -10 or -15C, which eliminates  much of the winter for me if I follow the rules.  I decided to mix in some synthetic motorcycle oil (40 weight) as motorcycle oils don't have the detergents that auto oils do (they need to do double function as clutch lubrication too).  

Back to efficiency - Rohloff claims a 96 or 98% efficiency of power transmission, depending on which set of the 14 gears you're in.  For the sake of averaging, I'll call that a 3% loss.  On top of that, I'm riding a Schmidt dynamo front hub which has a 3W drag to generate electricity.  So if I'm riding along at 250W, I'm actually only putting 239.5W to the ground.  Not too bad really, but that combined with the monster 29" wheel weight relative to a set of cyclocross tires has me sucking wind to keep up to my friends.

But this analysis overlooks one critical part I discovered this morning - my oil mixture's performance at cold temperatures.  Last night it was near -30C, and this morning it was about -25C.  I decided to put some additional lube on my chain, and with the bike leaning against a table on the outside porch, pedaled backwards with my hands while applying lube to the chain.  It was HARD to pedal backwards, like the hub was filled with grease rather than a fluid.  No doubt that hours of riding might soften it up a little, but I'm guessing that a thermal balance analysis has the outside air temperature winning the battle when it's that cold versus the friction heat generated.  I don't have any way to measure the power transmission loss, but for example when I spun the crank backwards with my hand at a crazy fast pace, maybe approximating 100rpm or so then let go, the crank stopped BEFORE making it a quarter turn past where I let go.  Good workouts in the offseason!

What does this tell me?  Rohloff hubs are awesome in the winter, I'm very happy with my entire setup but it's worth noting that low maintenance reliability and all weather functionality are definitely coming at the sacrifice of speed... fine if you're riding by yourself, but challenging if you're riding with people on external drivetrain bikes.