Comments on: Fuel Economy Tip – Roll the Windows Up

By: Jeff

Jeff — Mon, 27 Jul 2009 15:06:46 +0000

That’s a great study then, wow! It’s funny that you’ll see many other websites (including this one) claim that it’s better to leave your windows up based on no factual evidence (or very little). The treehugger study and the mythbusters study are the other two I have seen that have some research involved and those are the two that show ac off windows up is the best. I do appreciate this blog site letting us post comments though.

By: Ayall Sagi

Ayall Sagi — Mon, 27 Jul 2009 15:03:14 +0000

Jeff -

If i’m reading the graphs correct, it looks like they tested at three speeds all having the same results (that the best is AC OFF windows UP, followed by AC OFF windows DOWN, followed by AC ON (Medium Power) windows UP).
50kph = 30 mph
80kph = 50 mph
110kph = 70 mph

By: Jeff

Jeff — Mon, 27 Jul 2009 14:56:47 +0000

I also read somewhere that the compressor turns off around 70-75 mph, meaning it wouldn’t make a difference if you put your windows down or not. Did they test this in that speed range?

By: Ayall Sagi

Ayall Sagi — Mon, 27 Jul 2009 14:50:34 +0000

Jeff -

There was also a study using a sedan @ 30degC in the pdf i linked from the site you provided.

That study concluded same results, “that the best is AC OFF windows UP, followed by AC OFF windows DOWN, followed by AC ON (Medium Power) windows UP,” but it was a much closer race for “AC OFF windows DOWN vs. AC ON windows UP.”

By: Ayall Sagi

Ayall Sagi — Mon, 27 Jul 2009 14:42:50 +0000

Don’t be ridiculous Admin.

The on-going topic is clearly debating;
AC OFF windows DOWN vs. AC ON windows UP.

i don’t think anyone would ever debate;
AC OFF windows UP vs. AC OFF windows DOWN… that’s like debating the concept of gravity!
LOL.

By: Jeff

Jeff — Mon, 27 Jul 2009 14:42:21 +0000

The graph shows as speed increases gas consumed also increases. So like Ayall said, the worst you can do for your gas mileage is have your windows up and ac on (I guess some people have their windows down with ac on but that wasn’t tested), followed by windows down ac off, and the best is windows up ac off. It gets really bad over 80kph and takes off from there. Keep in mind, they were testing an suv at 30 deg C. These results are only for this situation, it may vary with other cars.

By: admin

admin — Mon, 27 Jul 2009 14:33:51 +0000

Is that not what I said?

By: Ayall Sagi

Ayall Sagi — Mon, 27 Jul 2009 14:30:42 +0000

Great Link Jeff!!
Provides a dash of the detail i was looking for, specifically the study found;
http://www.sae.org/events/aars/presentations/2004-hill.pdf

Admin – you are wrong.
The graph looks deceiving, as it’s showing gal/mile…. when we usually think of it as miles/gal.

The graph depicts, that the best is AC OFF windows UP, followed by AC OFF windows DOWN, followed by AC ON (Medium Power) windows UP.

By: admin

admin — Mon, 27 Jul 2009 11:58:09 +0000

Uh, Jeff, are you sure about this. According to the chart you provided — which gives good data by the way — it shows that gas consumption increases when a car’s windows are down vs. when they are up. I’m not exactly sure why you think the tip of “keep your car windows up” is wrong.

By: Jeff

Jeff — Mon, 27 Jul 2009 02:14:34 +0000

This tip is false, very false. Thanks for the bad tip, check out the graph on the middle of this webpage.

http://www.treehugger.com/files/2005/06/windows_up_or_d_1.php