Question about Air Conditioning and MPG

[WhoDatPanic]

How much does running the AC really affect the mpg in our tahoes ? does anyone know for sure? if it does or not i know i have heard it could be a myth or if it really is true ? Also how much could it drop mpg ? i usually get around 13 ish in city per gallon and never run the AC but its starting to get African hot here and would like to run the ac but scared it will significantly drop mpg's.

 

[ezdaar]

Run it, dont worrie about it.

If anything install some electric fans, or a simple pusher fan to keep the radiator thing cool when idle at lights and stuff.

 

[OBS Denali]

How much does running the AC really affect the mpg in our tahoes ? does anyone know for sure? if it does or not i know i have heard it could be a myth or if it really is true ? Also how much could it drop mpg ? i usually get around 13 ish in city per gallon and never run the AC but its starting to get African hot here and would like to run the ac but scared it will significantly drop mpg's.

They say running the AC uses the about the power of 1 cylinder from your engine. I dont know how that translates into mpg, but that may give you an idea of how much power loss you take when running it, and how much harder you're engine will have to work to replace that power to provide you with the same type of driving that you do.

 

[Gordy]

Not enough

To make me rather sweat my balls off when its 80 plus hot, and humid.


Thats like having an ice cold barley pop in your hand on a hot summers day, and afraid to drink it because you'll have to piss.


But to answer your question it depends on engine size as to how much it will effect MPG. The smaller the engine the more drag on the motor. Larger CI engines will see less of an effect. Either way you will get less MPG.


As for the 1 cylinder theory thats about 35 HP I find that hard to believe. That would be about 261110 watts, or 26.1 KW Most home central air systems do not use a quarter of that wattage.


Cheers

 

[Bedore]

Differences will be negligible. Run it.

 

[podwarrior63086]

they did a similar test on mythbusters about driving on the highway while running ac and driving on the hgwy no ac with windows down.it averaged out to be pretty close to the same mpg either way.

 

[waxworkz]

the rule i have always heard and go by is, anything above 40 mph and having your windows down is more wind resistance drag than the ac drags your engine. i run my ac all the damn time now that i have my efans, i must say it gets colder faster, stays colder and i picked up about 2 mpg with my fans and tune. i can also do 70 mph on the freeway, with the ac on, hauling a loaded 17 ft 4 horse trailer and 4 adults and 1 kid

 

[Jay]

The relationship is probably one cylinder at part throttle.

It takes 30-40hp to keep a modern full-size SUV at 65mph on a level road. Doesn't matter what engine is making that power, it just takes that much to overcome wind drag and tire friction to maintain the speed. To that point, in a V8 each cylinder is making 4-5hp.

FWIW, I've never seen more than 1mpg difference in running the AC. Traffic conditions (speed, congestion, number of stops, etc) will dictate mpg far more than the AC will.

 

[edgaranah1]

they did a similar test on mythbusters about driving on the highway while running ac and driving on the hgwy no ac with windows down.it averaged out to be pretty close to the same mpg either way.

Yeah i saw that show too. I always have the ac on I would rather pay a little more and be comfortable

 

[M3PO]

the rule i have always heard and go by is, anything above 40 mph and having your windows down is more wind resistance drag than the ac drags your engine.

This is what I have heard from several different sources. That said, the OP sounds like he/she might be talkingmore stop and go driving so he/she might not be reaching those cruising speeds. My guess is in stop and go traffic you might only notice 1-2 mpg loss.

I have no research to back this next statement up; this is just MY guess. I use the "recirculate" option when I use the A/C in hot weather. My guess is, if you are not continually pulling hot outside air, rather pulling the already cool air from the cabin, your A/C compressor doesn't have to run as much to keep the cabin at a set temp. I'm sure there is not much difference if any, but its only the push of a button