limited climate control question

[Tucson4runner]

did not find any threads on this so i thought id throw it out there please have mercy if this has been discussed or if this question is very very stupid. well ive got a limited 2000 and the ac uses electric fans to push the air. and i know that turning on the ac puts extra stress on the motor which causes less mpg. well because of these two things does that mean that it doesnt matter what level i have my ac on its going to affect my mpg the same? so if i have it on low or high it doesnt matter as long as the climate part is on cold its pretty much always on high? hope im making sense, if not ill try and think of another way to put it. all i know is in my old car that didnt have electric fans if i kept the ac on the low setting it hardly affected my mpg but if i put it on high i was getting like 3-4 mpg less. thanks in advance guys

 

[criera]

though relatively negligible, i would think the fan setting would in fact make a difference. If im not mistaken the additional power draw on the alternator causes more drag, resulting in less mpg. so more power drawn=alternator works harder=less gas mileage. I guess the question is what is the difference in power draw between low fan setting and high fan setting. Probably not that much once its running to begin with.

Anyways thats one of the reasons i put my daytime running lights on a switch.

 

[Tucson4runner]

sweet cuz lately ive been running it at cold but at the lowest fan speed. since ive got the ac on cold i dont think turning up the fan speed to high will make a huge difference. thanks!

 

[IanB]

I'm going the other way, and saying the difference will be negligible. AC lowers your fuel economy because the engine has to spin the AC compressor when you're using it, not because of any electronic fans that are activated. Having the temp set cooler will mean the compressor cycles more often, so that could affect economy, but fan speed won't make a difference.

 

[Tucson4runner]

thats what i was hoping because with the ac on cold my mpg hasnt really changed at all so knowing that i can turn it up full blast really helps. especially with all this AZ heat

 

[criera]

here is a relevant article on improving mileage. first two items address the ac system and how to optimize its use. the article doesnt reach the depth of other hyper-miling threads ive seen but it does offer suggestions ive not seen before. interesting read anyways. i doubt any one item makes a noticeable difference by itself, but if you adopt an all encompassing philosophy to your driving habits and practices, i bet eventually they add up.

9 Changes You Can Make to Your Car Right Now to Save Gas - DriveSteady.com

 

[TheDurk]

I'm going the other way, and saying the difference will be negligible. AC lowers your fuel economy because the engine has to spin the AC compressor when you're using it, not because of any electronic fans that are activated. Having the temp set cooler will mean the compressor cycles more often, so that could affect economy, but fan speed won't make a difference.

Actually it will, and you just gave the reason. Running the fan on high allows more heat to be absorbed by the evaporator, and brings warmer air to the thermostat, causing the compressor to cycle on more frequently. It makes much less difference if the compressor is already at max output, so that no additional compressor cycling is possible. Quibble aside, net difference is marginal--run the fan.