io333, no offense but I want to see a credible dispute by an independent company and not some joe schmo that did a couple of runs w/ and w/o the a/c on the hwy then posted the results on a forum... As far as I am aware thats a know fact and hasnt been debated, maybe there are a few cars that do not but generally speaking, this applies to most modern cars... It was even in my '96 altima's owners manual if I am not mistaken... Or you can just google it...

 

Actually, let me correct something. I am mostly talking about 4 cyl vehicles. As the displacement increases the less effect a/c has on your mileage. V8s get virtually no significant difference whether the a/c is running or not, period.

 

doesn't anyone watch mythbusters? they even did a test on a track, albeit going like 50, but they proved that windows open is better. and keep in mind how much drag a ford explorer can create.

 

i find that very hard to believe, car accessories are still engine parasites, no matter how big the engine.

 

You are right but they are not as significant of parasite. Ex: If you load your tc with 4 people and then you load a Lexus LS430 with the same weight you will see that the tc will have a substantial drop in mpg opposed to the lex in comparison to their regular respective mpg.

Also, at 65 or above (how most of us drive on the hwy) the drag is tremendous w/ open windows. Drag increases a lot faster than speed. I read somewhere that for a tc to go like 160 it will need around 600 horses to beat drag.

 

I did see the ford explorer thing, but it was regarding having no tailgate or having the tailgate down. They actually proved there that you LOST gas mileage with the tailgate down due to the "detached bubble" effect of the air. So the "air gates" are not only a waste of money, but can actually be a detriment to mpg. I havent seen the one regarding having the windows down

As far as drag.. the above is pure speculation. "Drag is enormous" doesnt really say anything since there are no numbers behind it. It really depends the car and the way it is shaped. Here is a good experiment for someone to do. Go out on the most calm day you can. and pick a long stretch of road. Accellerate to 80mph and let off the gas. Time the time it takes you to get to 50 mph. Do this on the same stretch of road in the same place 3 times to get a good average. Then do the same with the windows down. I would be interested in the result.

 

lol you need a wind tunnel to determine that there is a drag increase with windows open and closed at 65mph? If you are that interested in numbers you can google it and I am sure you will come up with some car that has numbers like that... p.s. Your test will not determine how much gas you are wasting but what effect drag has on our little engine in terms of acceleration, which has no direct correlation with mpg because there are more unknown variables if you do it your way.

Well I got to go, bye folks...

 

Just a quick note. I got 20% better gas mileage and a noticable hp re-gain out of cleaning my Oxygen sensor on the MAF. Just 2 screws to undo and a Q-tip with some rubbing alchohol is all ya need. You should notice the Oxygen sensor right away when you pull the MAF off the intake tube. I blew the sensor with some compressed air before re-installing the sensor but I'm just **** like that. I have about 30,000 miles and a K&N air filter.
My car feels reborn after this simple fix and would just like to pass this lil tidbit on to my peeps. Later all

 

They did another with the A/C on or windows open. I believe they did 2 of them. One on a test track and one on the road. I think the higher the speed the better off you are with the A/C.

http://kwc.org/mythbusters/2004/11/m..._catapult.html
Windows down vs. air conditioning
"Urban puzzle": it is more efficient, on a hot day, to run with the A/C on and windows up than to run with windows down (b/c of increasing car's drag).

Computer-based mpg measurements:

11.7/11.8 with A/C on and windows up
11.7/11.8 with A/C off and windows up
11.3 with A/C off and windows down
So, according to the computer, it's better to use A/C with windows up.

This was too quick and easy for TV, so they decided to stage a seven hour marathon, race-til-you're-empty duel, with Jamie driving an SUV with A/C on and Adam driving an SUV with windows down. Though, once the safety inspector intervened, it was no longer a seven-hour marathon, it was a bit slower (45mph instead of 55mph), and a lot shorter (only 5 gallons each).

Jamie's A/C car ran out of gas first -- Adam's windows down SUV ran for another 30 laps -- completely contradicting the computer mpg estimate. Computer estimate based on air flow into the engine, so it would appear that it is unable to properly model the difference between A/C and windows down.

Mythbusted

 

The A/C takes a certain amout of power. With a smaller engine this means it is using a larger percent of the total power. Lets just say it takes 10 hp just to make it easy since Im not looking it up. On something with a 100 hp engine thats 10% of the total power and it makes a difference. You will notice your car is much slower and uses much more gas. Move up to something with like 400 hp and that same A/C is only taking 2.5% which you really wont notice any difference.

 

My test will have NO measurement of how much drag effects our engine at ALL. Not sure how you got that idea since it is a COASTING test. My test will determine how much extra drag is added by opening the windows. That can be gathered by simply reading my post completely. My point is that you cant simply assume there is a "huge" amount of drag introduced by simply opening the windows. To make any type of comparison to running the ac with windows closed you need to know the effects of both. To properly (as well as reliably and scientifically) measure each component, you need to measure each one with the smallest number of other variables possible. So by starting at a certain speed, and coasting to a lower speed both with windows opened and closed you get an idea of how the windows being opened effects the wind resistance. By using simple physics you can determine from the numbers how much wind force at a given speed is introduced by using the initial speed, the ending speed and the time taken to change between the two. This gives you a number for decelleration due to wind resistance alone since all other factors remain the same.

To prove that you cant just assume the drag effect points back to my example of the mythbusters test between running a truck with and without a tailgate (which was also corraborated by some engineers). Running with the tailgate down can DECREASE your gas mileage. The slight "drag" created causes a detached "bubble" of turning air which actually increases the aerodynamics of the vehicle. To assume physical effects you have to take into account all the physics involved.

And emiller: thanks for the info on the other mythbusters test, very interesting!

 

wow i got 240~ last time.

100% city.. stop and go and flooring it when i get the urge

 

wow.

so i guess it's normal for the tc to go down the 200~ mile range on a full tank of gas.

but i thought we had a camry engine.

 

i get between 260-280...

i drive 8 miles too and from school....tahts a hard 8 miles :-D especially when im late..

work is about 25 miles away and traffic always blows.

 

First, engifeneer; your test is pointless because, A/C load on the engine is more or less consistent whereas drag is multiplied by speed. Ex: You may slow down from 70mph to let' say 30mph (these are hypothetical numbers) very rapidly but then you may coast at 10mph for a long time because there is not much increase in drag with windows open at that speed.

Second, the test conducted by myth busters was at a constant speed of 45mph (hardly hwy speeds, thats what I do in the city) opposed to 70mph (which I think most of us everage on the hwy)

Now to make my point; (This is quoted from Wikipedia.com)

"fluid drag increases with the square of velocity. When velocity is doubled, for example, not only does the fluid strike with twice the velocity, but twice the mass of fluid strikes per second. Therefore the change of momentum per second is multiplied by four. Force is equivalent to the change of momentum divided by time. This is in contrast with solid-on-solid friction, which generally has very little velocity dependance.

Another interesting relation, though it is not part of the equation, is that the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula. Since power is the rate of doing work, exerting four times the force at twice the speed requires eight times the power. However, with a doubling of velocity, the time taken to cover a given distance also halves. This means that the total energy used to overcome drag over a given distance only increases with the square of velocity.

Reference: http://en.wikipedia.org/wiki/Drag_(physics)

 

this is still going on? give it up! get with your congressman/woman if you're that worried about mpg!

 

Good thing I saw this thread...I installed my Injen CAI and noticed that I was getting like 20 less miles per tank. I thought that a tC's normal cruising range was like 370-400 miles...after readig this i feel better. I guess my mileage drop is due to my lead foot :D But yeah, I short shift now, and skp gears when can...anything to keep the revs down. Last tank I got 320 so I was happy. Driving normally I'll get like 270-ish

 

damn anything over 300mpg in a full tank is good for me.. my old car was 150 mpg per tank..

 

i've just hit 30,000 miles and my gas mileage has gotten better. on 87 octane im getting 366..
i usually avg. 330... lots of hwy driving though...

 

i dont know exactly how far it is but i made it from San Antonio to the border of Mexico on 1 full tank of super unleaded.... btw.. i got a pretty cool link here, it will tell you the cheapest gas of anywhere in your area code http://autos.msn.com/everyday/gassta...?zip=&src=Netx