Wondering why people complain that Yaris' cant get good mileage?!

[bkrownd]

Originally Posted by daf62757

You know, the difference between 41 and 38 MPG is not really that much. The creature comfort of cruise control and AC make it well worth the 3 or 4 MPG that these luxuries cost me.

YMMV. I will get out and push for 3 extra MPG. ;)

[gokartride]

AC isn't really a creature comfort here...it's life support!

[Kal-El]

I'd still run my AC even if it dropped FE by 25%.

If the cabin temp is above about 72 degrees, I run the AC.

[Yarisduder]

So what was said above is that if on my two best tanks I hadn't run the AC I'd have gotten about 50mpg? How much energy does it really require to run the AC? 1hp? 2hp? I doubt more than that, so I should probably see a mere 1 to 2% increase in fuel mileage if I turn it off. Thinking back though, my best mileage is with the air conditioner turned on, maybe it's because the fuel atomizes better in hotter weather? Maybe it's because I changed the engine air filter? It certainly has nothing to do with the AC.

Does the Yaris require the full power of it's engine to keep moving? Is it possible that the AC operates on extra power that would otherwise be wasted and therefore only affects your fuel efficiency when accelerating or driving very very fast?

[yarrr]

Originally Posted by Yarisduder

So what was said above is that if on my two best tanks I hadn't run the AC I'd have gotten about 50mpg? How much energy does it really require to run the AC? 1hp? 2hp? I doubt more than that, so I should probably see a mere 1 to 2% increase in fuel mileage if I turn it off. Thinking back though, my best mileage is with the air conditioner turned on, maybe it's because the fuel atomizes better in hotter weather? Maybe it's because I changed the engine air filter? It certainly has nothing to do with the AC.

Does the Yaris require the full power of it's engine to keep moving? Is it possible that the AC operates on extra power that would otherwise be wasted and therefore only affects your fuel efficiency when accelerating or driving very very fast?

On the freeway, having windows down creates drag which hurts your FE than having the A/C on.

And no, the A/C doesn't run on magical "extra energy." Just about every ounce of wasted energy has been engineered out of modern highly fuel efficient cars.

[Yaris Hilton]

Probably around 35 MPH is a break even point between having the windows open and having AC on. Above that I always close the windows and use the AC as needed. Window drag varies a great deal with the wind conditions, of course. Once I've spent the energy to cool off a hot interior with the AC, I'm unlikely to roll the windows back down. Keeping the AC on low recirculating doesn't take a lot of power.

[BailOut]

Originally Posted by yarrr

On the freeway, having windows down creates drag which hurts your FE than having the A/C on.

This is inaccurate. In both testing with our SGII's and as proven in the 3rd season of the Mythbusters television show, windows down is always more efficient than a/c at any speed.

In fact, with the SGII it is nigh impossible to read the drag hit of having the windows down, but turning on the a/c at any speed is an instant large and sustained hit to FE.

[daf62757]

Originally Posted by BailOut

This is inaccurate. In both testing with our SGII's and as proven in the 3rd season of the Mythbusters television show, windows down is always more efficient than a/c at any speed.

In fact, with the SGII it is nigh impossible to read the drag hit of having the windows down, but turning on the a/c at any speed is an instant large and sustained hit to FE.

I didn't see that episode, but I did a search on found this website.

http://green.autoblog.com/2007/08/29...-down-episode/

According to the website, windows down does hurt mileage. Just on a simple physics level, the air entering the cabin has to have some breaking action on the vehicle as the air has no place to displace. If you had the tail open, it could be a flow through action that might not effect the velocity of the car.

I am no expert on the matter....but I did stay at a Holiday Inn Express last night and will use my AC....because I love cold air and I am rich enough to afford the extra quarter.

[Yarisduder]

Originally Posted by BailOut

In fact, with the SGII it is nigh impossible to read the drag hit of having the windows down, but turning on the a/c at any speed is an instant large and sustained hit to FE.

Do you have numbers to share with us? How did you control your environment? Was the ground flat? What speeds, was there wind, etc?


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[BailOut]

Originally Posted by Yarisduder

Do you have numbers to share with us? How did you control your environment? Was the ground flat? What speeds, was there wind, etc?

There was a big thread on it that was lost in the hack, but as I said the Mythbusters found the same thing, as did the folks on CleanMPG, as did the folks on PriusChat, etc. In other words it has become common knowledge.

As for the test environment, etc., it simply doesn't matter. Windows down in any scenario is far, far more efficient than using a/c in any scenario. It doesn't matter if you're pulling into your driveway or cruising down a highway, rain or shine, winds or no.

Tinting goes a long way for avoiding a/c use. When combined with window vents it lets me keep the 35% front window on the sunny side cracked about 2 inches and have the shaded window fully down, or both windows down when the sun is directly overhead or to the front. Aided by the 6% tint on the rear windows and top of the windshield (the darkest allowed by local laws) it helps keep the interior much cooler than without any of these things. In stifling heat I run the fan (just the fan - no a/c) on the fresh intake setting to aid with circulation.

Despite living in a high desert region the only times I have ever run the a/c is when my wife experiences hormonal issues. None of my other passengers ever ask for it.

[yarrr]

Originally Posted by BailOut

This is inaccurate. In both testing with our SGII's and as proven in the 3rd season of the Mythbusters television show, windows down is always more efficient than a/c at any speed.

In fact, with the SGII it is nigh impossible to read the drag hit of having the windows down, but turning on the a/c at any speed is an instant large and sustained hit to FE.

uh.

http://en.wikipedia.org/wiki/MythBusters_(2004_season)

Myth statement
Running a car with air conditioning on is more fuel efficient than running with the windows down.

Status
Partly Busted

Notes
Tests were performed under varying conditions (55 miles per hour (89 km/h) versus 45 miles per hour (72 km/h)). Also, the 55 mph test was using a computer to estimate fuel efficiency based on air intake, not actual fuel consumption, and showed A/C was more efficient. The 45 mph test consisted of running the tank until it was empty, and showed open windows were more efficient. This experiment—or one like it—is sometimes cited by the Magliozzi Brothers on Car Talk when presented with this question.


http://en.wikipedia.org/wiki/MythBusters_(2005_season)

Myth statement
Running a car with air conditioning on is more fuel efficient than running with the windows down. (From AC vs. Windows Down)

Status
Partly Re-Busted/Partly Confirmed

Notes
The fundamental flaw in the MythBusters' test was that the point where the drag becomes powerful enough to inhibit a car's performance with windows down was inside their 45–55mph margin at 50mph. Going less than 50mph it is more efficient to leave the windows down, but going greater than 50mph it is more efficient to use the A/C.



The sad thing is I just pull stuff out of my ass most of the time, you write novels on this crap.

[KrazyDawg]

Originally Posted by BailOut

In fact, with the SGII it is nigh impossible to read the drag hit of having the windows down, but turning on the a/c at any speed is an instant large and sustained hit to FE.

That's good to know. I always thought 40-45 MPH was the breaking point between having the A/C and window open but I found out I was actually getting higher MPG on one fill-up with the windows open and 90ºF weather.

Does it make a difference if only the driver side window is open? I don't have power windows.

How much of a MPG hit do you take going from A/C level I to level II? What about when you compare no air to air on level II but with A/C off?

[Yarisduder]

I never drive with the windows open, and except for the last two tanks of gas because of a road trip all my driving is city driving.

[BailOut]

Interesting, yarrr, but that's not what is shown on the Mythbusters episode. My only mistake was calling it from 2003 rather than the revisit in 2005.

What they found in 2003 was so controversial that they revisited it in 2005 and got the totally opposite response. I'm not sure where the 50 MPG "barrier" idea came from as it's not in the episode (which I just watched again via Netflix) or on the Discovery web site. The only thing shown in the episode was that windows down beats a/c period, and this is what (I say again) consumer testing here on YW, CleanMPG and PriusChat have also shown.

If you don't believe me then get a ScanGauge of your own and go nuts.

[Yaris Hilton]

I can't believe windows down beats AC in EVERY condition, but I'm not about to buy a Scangauge and do a bunch of testing, either.

[Kal-El]

If gas was $10/gal, I'd still crank my AC. There's no way in hell I'm sweating my balls off on purpose. And I hate my windows down.

[STC]

Well, It's been downright HOT here in Central PA... hazy, humid and no breeze! There has been three days of +95 degree temperature and one of those days close to 100 F!

I've been using A/C more than my usual increments. Around 90% of the time!
I thought this would kill my gas mileage, but it didn't. My Yaris actually does great in the HOT weather. I filled up early this morning and to my suprise I got 49.524 MPG (495/9.995). My second best MPG and no trips... country driving mainly!

I'm taking a trip next week... Bring on the HOT temperatures... just for next week.

Cheers!

[bkrownd]

I had to turn on the heat for a few minutes yesterday. I wonder how it effects my MPG... :D