I suspect it's all that + maybe some little other things. The big problem I have with that is this. I use the engine when traveling 50+ miles at highway speeds, something I do maybe 5 or 6 times a year (at MAX, some years I don't take any road trips and just fly). Now the problem there is it's a constant speed, 70 mph, and with cruise control. The clutch will always be engaged. Around town in the cold down near 30 to 40 mph (which is where I feel this drag like chuggle) the engine runs only maybe 20 miles a week, and we're only cold enough to need that two or three months out of the year.
I fully expect by the end of my 3 year lease I'll only have maybe 1,000 to 2,000 miles on the engine with probably half of those at a steady freeway speed....