you mean ATF in the primary? Oh and I run half/half 10-40 and 5-30. It doesn't really matter on these bikes, but I learned from cars that a split of 5-40 or more (I've seen 10-50, and even 5-50) has reduced prolonged lubrication as they're full of polymers and MAGIC to achieve those ratings instead of pure lubricating stuff. On motorcycles that get their oil changed every 1,500 miles or so this doesn't matter, but on 5 and 10k cars the oil breakdown is too much.
I do agree with the thinner recommendation for winter, though. Kickstarting in the morning has been a bitch recently in sub-freezing temps.