Streamlined Prius garners more MPG

'as much as 7mpg savings'

Dyno screenshot or it didn't happen

Official fuel economy tests are done on a dynamometer. The reason is simple: there are so many contributing factors that affect fuel consumption that to get a repeatable result, you have to control as many as possible. That results, of course, in it being hard to achieve the raw dyno results. (The new EPA tests now include three 'worst case' tests - very cold ambient temperature, a/c on full, and rapid acceleration/high speed - which depress the overall results, making them easy to beat simply by not driving that badly, having A/C off or low, and doing your testing in summer/warm climate.)

Testing A/B/A on real roads to verify any fuel economy gain is very difficult, let alone stating an actual value, because of the changing conditions - you just can't reproduce it properly. If your road test got 53mpg, great! But don't compare it to the EPA's 46 combined, and calculate a 7mpg improvement, if you're not doing their test cycle under the test conditions.

Of course, on the dyno, the car doesn't move through the air, so the dyno has to be adjusted to simulate the wind resistance. Unless the manufacturer has actually done a lot of wind tunnel measurement, any recalibration of the dyno for the different aero pieces is guesswork at best.

See also Fuel saving gadgets - a professional engineer's view.

 

$3k for the full mod. that is a lot of fuel, and even a lot more as a delta fuel saving. Never recover it, or, almost never 370k miles.

 

They touched every surface, including underneath, to reduce the 2010 Prius Cd to 0.25. They even shaped the airflow coming out from the front wheel wells to reduce turbulence when it meets the side stream.

What's the Cd with all that add-on stuff?

 

Well, it's ok, but personally, I like the looks of mine & don't mind spending a little more on gas.

 

Um..... you can't measure aerodynamic improvements on a dyno. You would have to put the car in a wind tunnel and measure drag. .

 

Nice idea.

But for the wheel skirts, the phrase enhance the streamlined "appearance" suggests it doesn't actually improve the Cd. It seems to stick out just a bit so I'm guessing that's for appearance only (altho you would think it would help if done right). From the website however (bad grammar/spelling and all):

I'm not going to do the math conversion to MPG on a Saturday, but that's about 12%.

But there's apparently no changes underneath the car, which to me could use the most improvement. And of course, removing the rear-view mirrors and putting in a small camera and interior LCD screen should make a difference as well.

 

Oh, no, I used 10 mpg benefit for my calc. Now, it will take over 400k miles to break even, not counting opportunity costs of that $3k.