Consumer Reports says windows down does not effect mpg

[marccbr]

Just read this article on green car reports, http://www.greencarreports.com/news/1077286_busted-7-things-that-wont-improve-your-gas-mileage" onclick="window.open(this.href);return false;. I find it hard to belive. They even say that the tires our cars have does not do much to improve the mpg. What do you guys think?

 

[smkettner]

I find anything to do with vehicles out of CR hard to believe.
CR is better with vacuums and laundry soap.
JMHO

 

[TomT]

I disagree. I think that do an excellent job with vehicles overall.

Other tests have shown that, on an AVERAGE car, LRR tires do in fact make a very small difference in MPG. Likewise, the added drag from the windows being down... Mythbusters did a windows down test some time back and came to a similar conclusion on a big old sedan.

I find anything to do with vehicles out of CR hard to believe.
CR is better with vacuums and laundry soap.

 

[thankyouOB]

1, 2, 3,

here come the consumer reports bashers.
are they all neo-nascar people?

 

[garygid]

If the car's aerodynamics are important to its performance,
then the windows down will most likely affect performance more.

 

[TonyWilliams]

This is so pitifully easy to test, I find it amazing that we, no doubt, will have pages of banter.

The easiest way, that flat landers can't do, is find a hill that you can roll down in NEUTRAL, starting from a stop, preferably getting to 60+mph. Mark where the car stops at the bottom. Now, with EXACTLY the same conditions (tire pressure, temperature (for air density consistency), wind, etc, roll the hill with just the back windows down (where I predict the most drag is) and I think you'll find some difference.

Do the test several times to prove that you can repeat the results consistently.

 

[camasleaf]

This is so pitifully easy to test,....

What about set cruise control at 70 mph, on a flat freeway. Watch the power consumption with windows closed than open the windows. Will the change be too small? Maybe the instant mpkwh will see a difference.

 

[TonyWilliams]

This is so pitifully easy to test,....

What about set cruise control at 70 mph, on a flat freeway. Watch the power consumption with windows closed than open the windows. Will the change be too small? Maybe the instant mpkwh will see a difference.

The instruments available to you are going to be tough. Maybe it would work.

With a Gidmeter or future LEAFscan device, you could monitor battery amps on a level road, but it bounces around a bit, even on level ground. If I didn't have a convenient hill, I'd use the Gidmeter.

 

[GeekEV]

From the demo I saw of LEAFScan tonight, it is very sensitive and you'd easily be able to see the difference with it.

 

[TonyWilliams]

From the demo I saw of LEAFScan tonight, it is very sensitive and you'd easily be able to see the difference with it.

Gidmeter and LEAFscan should be displaying the exact same amp data. It comes from the car, and is merely displayed at either device.

 

[adric22]

The really important question is not whether the windows down makes a difference. After all, I'm sure it does. The real question is, given the choice between running the A/C or having the windows open, which uses more power? I'm 100% convinced that in regular city driving conditions the windows down is a better option for energy savings. I'm not as convinced for highway driving, though. I've been meaning to do some tests.

Now. Also it must be worth mentioning that a lot of people think the A/C doesn't consume much power. But those of us here in Texas and I'm sure those in Arizona would beg to differ. With it being 105 or hotter outside, the A/C compressor has to run pretty much constantly. Sure, during the spring or fall the A/C will cycle on and off a lot and probably doesn't use all that much power. But the Texas Summer is a different story. I pretty much do not use my A/C at all in any car I have owned, except for when it hits 100 degrees or higher. Even then, I roll the windows down for my morning commute. But the evening commute is just intolerable to me.

I've been meaning to do a test where I drive the same stretch of highway a few times with the A/C and then a few times with the windows down and watch the energy consumption and see what happens.

 

[Pipcecil]

I honestly think the window vs A/C has more inputs than we think. A car with horrible drag won't notice much of a difference with windows down or up. But take a highly efficient aerodynamic car such as a volt or leaf and when you disrupt that, the effects should be more pronounced. As for the A/C, both the leaf and volt's are really efficient will providing very cool air, even in Texas. The rental I have atm (mazda 6) can be blowing full force and I never get cold enough to turn it down.

So different cars have different A/C efficiencies and more aerodynamic cars probably benefit greater from having the windows up.

 

[EVDRIVER]

I disagree. I think that do an excellent job with vehicles overall.

Other tests have shown that, on an AVERAGE car, LRR tires do in fact make a very small difference in MPG. Likewise, the added drag from the windows being down... Mythbusters did a windows down test some time back and came to a similar conclusion on a big old sedan.

I find anything to do with vehicles out of CR hard to believe.
CR is better with vacuums and laundry soap.

And myth busters is so scientific :lol: In addition not all cars are designed the same so some aerodynamic cars behave differently.

 

[EVDRIVER]

I disagree. I think that do an excellent job with vehicles overall.

Other tests have shown that, on an AVERAGE car, LRR tires do in fact make a very small difference in MPG. Likewise, the added drag from the windows being down... Mythbusters did a windows down test some time back and came to a similar conclusion on a big old sedan.

I find anything to do with vehicles out of CR hard to believe.
CR is better with vacuums and laundry soap.

And myth busters is so scientific :lol: In addition not all cars are designed the same so some aerodynamic cars behave differently.

 

[DaveinOlyWA]

1) CR is generally transparent about how they do their tests and there is plenty of variance since its different drivers, etc. but they usually run each test enough to level out the results. testing a single vehicle without mentioning variables is not something i would bank on.

2) Mythbusters is great entertainment but most of the shows (and i have seen most of them!) do not perform tests that meet my expectation of scientific accuracy. having a few people who are "good with their hands" fabricating various experiments is not what i would consider to be a definitive answer.

as far as wind drag. it does HIGHLY depend on the aerodynamics of the car and problem with ones that have good dynamics is that low frequency buffeting sound we tend to hear frequently if the right combination of windows are not up or down.

i prefer the windows to be down even on relatively hot days. even when i plan to use AC i always roll all the windows down for the first few minutes just to remove the super hot air. now that is me alone. most of the time, rolling down windows with passengers is not an option because of some unknown hair issues (what hair i have is cut very short...)

on the tire thing "properly inflated" needs to be defined because i found that tire pressure is by far the biggest factor in your MPGs

all in all, i have to say that despite this new info from CR, the real definitive answer (Which CR ends their article with) is "YMMV"

 

[Herm]

In an ICE, LRR tires will often pay for themselves completely if you keep them long enough. If CR did not see savings then perhaps the tires were not broken in... obviusly if you are a NASCAR driver and your tires wear out in 30k miles then dont bother, but if you tires last 60k or more then it would be worth the extra expense.

 

[garsh]

Mythbusters is great entertainment but most of the shows (and i have seen most of them!) do not perform tests that meet my expectation of scientific accuracy.

Obligatory xkcd comic

 

[GeekEV]

From the demo I saw of LEAFScan tonight, it is very sensitive and you'd easily be able to see the difference with it.

Gidmeter and LEAFscan should be displaying the exact same amp data. It comes from the car, and is merely displayed at either device.

I did not mean to imply the Gidmeter wasn't/couldn't. I just haven't seen/played with one.

 

[SanDust]

It's just senseless. For example, one "busted myth" is that low rolling resistance tires are always better. How is this myth busted? By proposing that you don't properly inflate the low RR tires and that you purposefully drive so as to get low MPG. That's like saying that you won't get better MPG with a more aerodynamic car if you put a roof rack on it.

Then there are the selective characterizations. A 3 MPG change effected by running the AC is so large that it's "shocking". On the other hand low rolling resistance tires don't matter because they only add "a few MPG". Basically it's the same MPG difference but if it makes their point it's "shocking" and if it hurts their point it's dismissed as "a few" meaningless MPG.

Unimpressive.

 

[dandrewk]

It really depends on the car. For some, windows up or down could make a big difference. For others, though, little or no difference.

IIRC, the Leaf's odd shaped headlight enclosures were designed to improve aerodynamics over the side view mirrors. If so, it's hard to believe windows rolled up/down not having a large effect on drag.