couple notes on gas conservation
Jul. 11th, 2008 09:01 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
tagryn* The 55 MPH speed limit is getting traction again thanks to the current high fuel prices. As it happens, while 55 MPH is the optimal speed point for fuel economy, this graph shows that there isn't much of a difference between 40 MPH and 60 MPH. However, once you go past 60, the fuel economy really starts to suffer (and it also depends on the vintage of your car, presumably because of better aerodynamics of more modern cars).
This article explains why the 55-MPH phenomena happens:
* I always thought that driving with the air conditioner on was a way to waste gas, but actually driving with the windows down is more wasteful than having the AC on with the windows up once you get past 45 MPH, again because of extra wind drag. The recommendation is to open the windows when you first get into the car to clear out the superheated air that's collected inside (due to solar heating), then after a couple of minutes when the temperature has equalized inside and out, roll up the windows and turn on the AC. And don't forget to turn the air circulation to recirculate, so you aren't constantly blowing in hot air from the outside.
This article explains why the 55-MPH phenomena happens:
Why does driving more slowly save gas? It’s a matter of drag. Your wind resistance increases as a square of your speed. So at 80 miles per hour, the wind resistance is more than twice what it would be at 55 miles per hour, because 80 squared (6,400) is more than twice 55 squared (3,025). But at 80, you’re only traveling 45 percent faster than you are at 55.
* I always thought that driving with the air conditioner on was a way to waste gas, but actually driving with the windows down is more wasteful than having the AC on with the windows up once you get past 45 MPH, again because of extra wind drag. The recommendation is to open the windows when you first get into the car to clear out the superheated air that's collected inside (due to solar heating), then after a couple of minutes when the temperature has equalized inside and out, roll up the windows and turn on the AC. And don't forget to turn the air circulation to recirculate, so you aren't constantly blowing in hot air from the outside.
