Yes a little wind can make a big difference. A 10 mile head wind is nearly the same as driving 10 mph faster, a tail wind 10 miles slower. That's a 20 mph difference one way vs. the other.

I have a 5 mile stretch due east going to work and I see my scangauge climb steadily from around 20mpg to 30+mpg during this stretch. On the way home it is either steady or drops 1-2 mpg on this same level stretch. It's all because of the wind though you wouldn't think it was "windy".

For some reason a cross wind seems to hurts the FE a lot too?