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2013 Kia Rio Lx+
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Discussion Starter · #1 ·
I've been observing the fuel consumption when using air Conditioning. I can't really dictate the fuel consumption when using AC and driving .
ALTHOUGH
I have tried on several different occasions measuring the difference when coasting in neutral after the car has been driven and warmed up. When i coast in neutral i have 1.6-1.7L /100km and when i coast in neutral with AC still operating I am using 2.1-2.2L /100km. Basically meaning that when in neutral my car uses 31% more fuel with AC on.

Wondering if anyone out there has been able to do a direct comparison like this when driving at highway speed. I don't have any leveled straight highways here where I can keep a steady speed without RPM changes.

Once I think of a straight highway I am going to try to find the average fuel consumption on that stretch when 1. Using AC 2. Using open front windows 3. using neither.

Also another question. Does any tech savvy person here know 100% if the level of AC makes a difference fuel Fuel consumption. Such as AC on speed 1 VERSUS max speed
 

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2013 Soul+ Shadow, 1970 Opel GT 1.9 CIH 4M
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The MAX A/C position will always provide the best gas mileage as the system only has to cool re-circulated air so the compressor is operating under less load. Note, however, that this has nothing to do with fan speed; just the "MAX A/C" control position that forces the system to use re-circulated air.
 

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2012 Kia Rio 5-Door LX
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Actually, I thought that on highway it would not be very efficient to have the windows down over the running AC and most of the time in city traffic I am running with windows down and AC off so I guess I wasn't completely wrong then.
 

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Discussion Starter · #5 ·
thanks for that article. Informative. Only problem is that their tests were done with big V8's lol.

I'm assuming that the load AC puts on our engines vs those large engines is much different. I would bet its much more of a strain to our engines and decreases our mileage by way more than 10% if a V8 engine is only affected by 10% lol.
 

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Other problem is that windows down might not work very well if you have temperatures of 90F or above (30C +) outside unless you're used to it.
 

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Cerato S Hatch Auto
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It's generally thought that AC sucks a couple of MPG from your consumption; about 5-10%. That certainly seems to be the difference between summer and cold season fuel consumption where I live.

That seems about right; only about 20 kW required to keep the car running at cruising speed, while AC drain is probably about the same as a domestic unit; 1 or 2 kW. Obviously depends on outside temperature and degree of cooling required. As with domestic situation, fan speed has little influence on power consumption.

http://wps.aw.com/wps/media/objects/877/898586/topics/topic02.pdf
 

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Discussion Starter · #10 ·
Yeah i know car technology changes every year so i'm basically looking to see if anyone has found an article/study done in the last couple years that dictates the difference for "windows open" VS AC on full (for 4 cylinder cars) ..... and also if Fan speed from lowest to highest has any difference on the fuel consumption used on the AC .

As of now I'm keeping my AC on speed 2 because i am worried such small engines will be affected a lot by AC .

I previously had a 1.9L Saturn 4 cylinder .... and when my AC was on full speed in that car it was easily 20% worse on gas.
 

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20% seems a lot; it must have been more than fan speed to do that.

Having "windows open" is not an option if you really need AC. I can't imagine anyone making such a comparison. Even when it's fairly cold, the AC stays on to provide circulation/ventilation rather than suffering wind buffeting. Windows are only opened to expel really hot interior air after standing. It can be 60ºC some days.
 

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Discussion Starter · #12 ·
20% seems a lot; it must have been more than fan speed to do that.

Having "windows open" is not an option if you really need AC. I can't imagine anyone making such a comparison. Even when it's fairly cold, the AC stays on to provide circulation/ventilation rather than suffering wind buffeting. Windows are only opened to expel really hot interior air after standing. It can be 60ºC some days.
Yeah my saturn SC1 was amazing on gas. It was like a 100hp car it was as good on gas as the older honda civics even though it wasn't marketed as that . When the AC was on in that car it literally felt like it burned 30% more fuel but i know it couldn't be that high so I just said 20%. It was a 1998 though so maybe some belts or parts were really old and causing more strain than they should have. I'm not sure, i'm not a professional on Air Conditioning.
 

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I'm losing 4-6 mpg driving only freeways. My best is 44 but my average is 38 without ac, 34 is my average with ac.

Rick
 

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2013 Soul+ Shadow, 1970 Opel GT 1.9 CIH 4M
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Yeah my saturn SC1 was amazing on gas. It was like a 100hp car it was as good on gas as the older honda civics even though it wasn't marketed as that . When the AC was on in that car it literally felt like it burned 30% more fuel but i know it couldn't be that high so I just said 20%. It was a 1998 though so maybe some belts or parts were really old and causing more strain than they should have. I'm not sure, i'm not a professional on Air Conditioning.
#50

You are correct about the SC1 Gas Mileage. My son had one before he bought his Fiesta and I could not believe the gas mileage he would get with this SOHC Auto! His normal fill-up was 38+ MPG :D

It still blows me away, however, how frugal the SC1 was on gas - you used the exact word that comes to my mind - AMAZING! Saturn never took advantage of advertising the outstanding gas mileage on this car. This was one of the few cars in history where the mileage rating on the sticker was actually LESS than the "real life" rating.
 

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thanks for that article. Informative. Only problem is that their tests were done with big V8's lol.

I'm assuming that the load AC puts on our engines vs those large engines is much different. I would bet its much more of a strain to our engines and decreases our mileage by way more than 10% if a V8 engine is only affected by 10% lol.
Yes, but driving with the windows down at speed increases the drag so much, that it's possible the engine is working even harder than if the AC was on. With the windows down at speed, It's like that car is a parachute with a tiny engine trying to keep the whole thing going.
 
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