Dan writes about fuel economy experiments in his RV-7.
It’s interesting that he managed to get 35.4 statute miles per gallon out of his airplane. With a slight headwind, no less.
I’ve never seen more than about 20 mpg out of a Cirrus, even with a tailwind. That’s on par with far draggier airplanes like the strut-braced Skylane.
For such a slick airplane, that’s surprising. But perhaps it shouldn’t be. After all, Dan’s RV-7 is extremely light. The Cirrus aircraft are quite heavy, up to 3400 lbs on departure. So even with 50% more horsepower, the Cirrus still comes up short on a hp-to-weight ratio.
Dan’s experiments and my observations with the Cirrus just reaffirm my belief that drag reduction only gets you so far. If the airplane is heavy, it won’t matter how much aerodynamic improvement you make, it’ll never reach a respectable level of fuel efficiency. So if $6.00/gal. fuel prices are a concern, the moral is clear:  keep it light.