"5 Driving Myths That Cost You Money"

[shinlee]

uh...it's been proved time and again that riding with your windows down INCREASES mileage vs. using the a/c.... Hell, I've done this testing myself. Anyone can. Next time you go on a long road trip, and know you'll be stopping 3 or 4 times, start out with the a/c on the WHOLE trip, and calculate that mileage, then fill up and roll the window down, and calculate that whole trip and compare. Almost 6 mpg difference for me

[malibuguy]

Originally Posted by shinlee

uh...it's been proved time and again that riding with your windows down INCREASES mileage vs. using the a/c.... Hell, I've done this testing myself. Anyone can. Next time you go on a long road trip, and know you'll be stopping 3 or 4 times, start out with the a/c on the WHOLE trip, and calculate that mileage, then fill up and roll the window down, and calculate that whole trip and compare. Almost 6 mpg difference for me

you gotta use the A/C differently...having the windows down even a little bit increases the aerodynamic drag, it makes a complete mess of airflow over the back half of the car

i pulse my A/C use & don't see much of any reduction of fuel mileage unless i leave it cranked the whole time

[why?]

Originally Posted by shinlee

uh...it's been proved time and again that riding with your windows down INCREASES mileage vs. using the a/c.... Hell, I've done this testing myself. Anyone can. Next time you go on a long road trip, and know you'll be stopping 3 or 4 times, start out with the a/c on the WHOLE trip, and calculate that mileage, then fill up and roll the window down, and calculate that whole trip and compare. Almost 6 mpg difference for me

You are right for people that keep the AC on all the time.

The reason this myth started is some smarter than everyone else engineer did the quick calculations on the air drag, and ignored the drag and gas used by the a/c compressor. When you take that out, it looks true.

But as you noted, real life isn't theoretical mathematics.