Originally Posted by
threeighteen
Gearing has EVERYTHING to do with fuel burn in a car, and has an almost exponential effect on your fuel burn as speed increases.
When I raised my final drive ratio by .15 (a noticeable, but small change), fuel mileage at higher speeds dropped by about 7 mpg. Drag does play a significant factor, but gearing in a vehicle is much more of a factor than you account for.
I'm almost curious to see what would happen if I dropped my final drive down by .45, I might even have the proper unit in my garage, but it would rob my acceleration by a noticeable factor.
RV10 published stall speed is 57 mph statute, which equates to under 50mph nautical. You could certify the RV10 yourself if you wanted, you'd just have to shell out the clams to buy a few kits and build them all the same way and then get a type certificate from the FAA.
As for airplanes vs cars, theres no doubt you can make cars more efficient. Several of the newer diesels are capable of more than 100mpg if driven properly, however airplanes can be made comparably efficient. Klaus Savier did a 1985 sm transcon in his two seater VariEze, using only 25.8 gallons, that's about 77mpg, he's been known to hit almost 100 mpg in competitions as well.
I agree with everything here, just not the 25mpg at 110mph. I got 27mpg in my big V8 a few weeks back on a 750mi trip (one day), 26.6 the next day over 650mi the next day. People are usually amazed I can get that out of this brick of a car, but it's a combination of the 6th gear ratio and really knowing how to squeeze the mileage out (minimizing stops and starts, using the car's 1-4 gear skip shift feature, avoiding unnecessary accelerations, etc). It turns 1700rpm for about 70mph, and yes, that does make for decent mileage. On the flip side, I've owned a few "fast" cars now, any time you get to speeds like what you posted, you burn a TON of fuel, I also know people that own the same car that I do that can't figure out why they get more than 13-15mpg. I've gone fast in a big V8, a much smaller 4cyl turbo, and a few in between. When you "cruise" at those speeds, you can almost watch the fuel gauge move the entire time. If your gearing is such that you can cruise at 70mph at the rpms I listed, it can be difficult to accelerate to those speeds (in that gear). The drag going from 70, to 80, to 90, to 100 and then faster is huge. It's not linear, as we know, so it's not going to cost 2mpg for every 10mpg over 70, it has a huge effect at 110mph in a car.