Two brands of the clear plastic jugs: Clover Valley Distilled Water (from Dollar General) compared with the Ice Mountain Drinking Water (from WallMart) have different aerodynamics. The Clover Valley gallon jugs compare quite favorably because the side of the blade that would resist turning in the direction that is being pushed or cupped from the prevailing wind side -- that resistance side is quite "slippery" to wind. In other words, the resistance side allows air to slip past it with what seems to be the least resistance.
On the other hand, even though I was quite excited that the Ice Mountain jugs might have two blades per bottle instead of the normal one blade, it turns out that the resistance side is either flat or concave, producing too much resistance to the prevailing winds, ultimately. I have not yet put this to a physical test, though. It is just by looking at the first two blades that I cut off an Ice Mountain bottle that gives me this impression. I do not even feel it worthwhile to prove my assertion with a physical experiment.
Perhaps I'll post pix after the sun comes up, lol....