FWIW, my Ram (4.7) cranked just a shade longer during the cold snap last week. Literally like 2-4 more compressions before lighting off, but its usually so predictable that I noticed the difference. Seemed to go away with the next tank of fuel, so I tend to agree its probably more related to "summer" gas in cold weather than anything else. Personally, I'd tolerate the slight extra crank for the better performance (and less vapor stink) of "summer" gas year round. Not to mention that in my area we get the occasional 90-degree day during winter and "winter" gas wreaks complete havoc on carbureted cars (and even causes driveability problems on some EFI vehicles) on those days.