Anonymous99

Hey guys!

I was reading something online yesterday and happened upon a guy saying that if you're using your car AC, the temperature and fan speed don't matter in terms of how much gas your AC is consuming. The explanation was that the fan belt isn't connected to the motor and hence turning up the fan speed does not work the motor harder.

Does anyone have any insight into whether or not this is true?

My whole life, I've left the fan on the lower settings to try to save gas...

MCDavis

The A/C compressor is the main culprit to the majority of the draw/load on the engine. The fan speed does present an electrical draw, but it's likely so low on the scale of parts on the car presenting an engine load that you should not notice a MPG drop between low and high settings.
The electrical draw from high as compared to low, is probably less than that draw coming from the headlights being on.

Basically, the compressor should be presenting the same load on the engine regardless of fan speed.

KillerG

the air conditioner gasoline drain is so minimal and so insignificant that you would need a calculator to crunch the numbers and get accurate savings, so do yourself a favor and keep it on the highest setting whenever you feel like it, theres really no downside unless you are trying to hypermile

I also remember reading an old car and driver article or something where they dynoed a bmw z4 with the a/c on and off and concluded that you could liberate one horsepower (1!) with the a/c off. Keep in mind that would be even less on our smaller engine i believe...



tl;dr: push the a/c button off for extreme turbo boost

misu

was the radio volume really low for the same reason?

joking aside what about temperature settings, does the compressor go off once it reaches the right temperature?

I used to have a civic si and the power drop was significant when the AC was on.

pinatubo

I don't know the difference between AC FAN HIGH and AC FAN LOW but there's significant difference between AC ON and AC OFF; not only it consumes more gas but also make the car weaker (power draw off), very slow acceleration, slow response, .... BUT that doesn't stop me driving my car in the most comfortable condition. Set it to the temp. that you feel best and go with it.

etzero

I also noticed recently the performance hit when the AC compressor kicks in. There is nothing scientific about it, but if you set your panel to show instant MPG it will literally show a 5MPG drop when it cycles on. Do this at highway speeds w/cruse control on and it is very easy to see. Changing the fan speed didn't effect it.

Also it seems the compressors cycles on and off very frequently in this car.

Anonymous99

Reasonable point on the radio volume, but I've rationalized that with my mp3 player; the charge doesn't change based on the volume level I set it to... It did seem to me that more comfort would be more money in terms of the AC, but I'm quickly seeing that I'm wrong about that...

I guess the new question would be whether or not there's a difference in gas consumption with the temperature on 58 with high fan vs 75 with high fan.

misu

I would say if it's 90 degrees outside the lower the temp the higher the gas consumption just because the compressor will stay on longer periods of time. Also the smaller the engine the more noticeable power loss will be when AC is on.

I remember reading somewhere that AC off and windows down uses about the same as AC on windows up, it was for a truck but it's interesting.

ed_423

i've read on an yahoo article that with the newer cars, having ac on wouldnt really significantly kill MPG. but then again..its an yahoo article so who knows.

i have my windows down most of the time just to "save gas" though, but in reality i just dont want to get caught for my tint LOl

Professor

I remember having a heated discussion with a friend about the pop-up headlights on my Prelude... I said that the gas mileage may be spoiled abit due to aerodynamics (at 40 mph ) but battery drain ain't going to do crap to the mileage.

risc

I recently did a trip from Oakland to LA.

AC on the whole time since outside temp was between 80-93 degrees.
Left at 3:20pm and arrived 9:30pm with 2 stops.
Cruise control most of the way set at 75mph.

36mpg