Hello! I recently bought a Yakima rack (50" corebars, 46" wind fairing, baseline towers) and cargo box (Skybox 12) for my 2007 Prius and was wondering if anyone had advice for better efficiency. This week I went on my first trip with the new rig to Baxter State Park, 300 miles round trip with over half being 75 mph highway driving. On the way there I made 34 mpg in the rain, and 37 mpg on the drive back in dry conditions. I, of course, knew that there would be a loss in miles per gallon with the addition of these accessories and am completely comfortable with that; I love my average 48-52 mpg but I also love adventures with lots of gear and was curious as to what I might be able to do to get the most out of my gas. I saw postings on here from people that were managing to have an average mpg in the 40s with similar racks and cargo boxes.
Drive slower. Aerodynamic drag is a product of air density (which you can't change), area perpendicular to flow (which you can't change without removing the box and rack), drag coefficient (which you can't change without removing the box and rack), and the square of velocity. It's the one parameter you have control over...without removing the box and rack.
