Traveling east - west on I 80 and I 90, everything was going great... getting just over 40 MPG.... then I took I 29N to go from I 80 to I 90 after Chicago, turned left onto I 90 in SD and ran into the most obnoxious headwinds I have ever experienced. Mileage went from in the 40's MPG to 28 MPG in about 10 seconds. Spent the next bunch of hours riding at about a 15 degree lean angle on the bike, with my torso resting on the fuel tank. In addition to the gazillion MPH steady wind, it was gusting up to about three gazillion MPH. I 80 is a fantastic highway, and SD is a beautiful state IMO but I gotta' say, the ride through, three times out of four total, was truly awful.
Brian
Not only which way it blows, but also how hard it blows.
Hate to admit it, but one trip with the camper trailer into a nasty headwind got no better than 6 mpg out of the old Suburban. Usually average about 10 mpg towing the camper, around 18ish w/o.