Fuel Economy and Air Conditioning

Hey All,

I have an 5-speed '11 Aveo LS which I had the dealer install A/C. I know that A/C tends to be parasitic, but I was curious if anyone knew by how much?

I just ran a 300 mile highway trip @ 75 mph w/ A/C 4 passengers and a cooler and got 27.5 mpg.

Today I ran a 94 mile highway trip at 64 mph w/ A/C and just myself and got 29.4 mpg.

I feel this milage is extremely low considering I had an 2.5 Altima S as a rental and I did 75 with A/C and got 32 hwy. I am just curious if this sounds right for other Aveos with A/C?

If its new thats part of the issue, new cars need to be "broken in" first then the MPG starts to climb. It is difficult to say how long before you will see an increase in MPG but running the A/C has little effect on overall MPG. The big thing is the speed your driving at( 65, 75, 85mph) and you will see your MPG drop significantly. Also dropping the added weight will also help improve your MPG. All in all your new car will not get your EPA estimated MPG at the begining. I have an 08 hatch (auto running A/C) I get about 315 miles out of the tank so I still need to figure it out but its around 28-30mpg at 65-75 with big elevation changes.

Thanks for the reply redrob! I have ~1000 miles on her, so I am passed GM's break-in period, but I had heard that initial mileage is usually not so good. Usually when would one see improvements?

with the windows down, 80-85 mph, mostly highway (>80%) I got 32 mpg with my last tank.

the '11 has a slightly taller 5th gear, so you should be able to do better.

ac does take up to 15-20 hp.. on a bigger engines its less of a drain.. keep in mind there are a lot of factor to fuel economy than just engine size, epa estimates, etc.

I lose about 2 mpg when I use my a/c. I average 320 miles for 10 gallons, when I use the a/c i get roughly 295 for 10 gallons

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Originally Posted by redrob

If its new thats part of the issue, new cars need to be "broken in" first then the MPG starts to climb.

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I've heard this nonsense repeated before, but never is there any proof offered. It sounds like something a dealer would say to get you to go away and stop complaining. Please explain how and when this magical event of "then the MPG starts to climb" is supposed to occur.

My test, conducted using a ScanGauge when the car was still practically new, recorded 37 MPG @ 65 MPH with the A/C on, on a level highway, determined over a 20 mile trip. As soon as the speeds are lower than 50 MPH (owing to the A/T not being in lockup mode) the MPG drops enormously.

This car gets wonderful MPG if you can always drive exclusively at highway speeds of over 50 MPH and avoid all other types of driving.

And as for the "broken in" myth, now that my car has 8000 miles on it the MPG is still the same as the day it was bought new.

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Originally Posted by paulsaveo

I lose about 2 mpg when I use my a/c. I average 320 miles for 10 gallons, when I use the a/c i get roughly 295 for 10 gallons

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Your milage sounds fairly close to mine so I feel a bit better seeing that - thank you! What speeds are you typically driving?

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Originally Posted by petrified.rabbit

...ac does take up to 15-20 hp.. on a bigger engines its less of a drain.. keep in mind there are a lot of factor to fuel economy than just engine size, epa estimates, etc.

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If what you're saying is true, that could be up to a 20% performance loss on this vehicle which would take 35 mpg down to 28 so that makes sense.

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Originally Posted by Thymeclock

I've heard this nonsense repeated before, but never is there any proof offered. It sounds like something a dealer would say to get you to go away and stop complaining. Please explain how and when this magical event of "then the MPG starts to climb" is supposed to occur.

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Its nothing that I have gone into researching.............its just something that I have heard as well. When I would get a new car it wasnt to save gas so I wouldnt check to see what my MPG was and when I bought this car (to save gas) it was used. I do remember there being some rumors about engine shavings and impurities in the oil for a new engine but I dont know if that affected MPG or if it is even true( again I dont care enough to go do some scientific research) to begin with. BTW do yoou have any info other than your experience that confirms that this "myth" is just that or do you just say this casually?

To the OP, I get very similar MPG in a '10 sedan. 50-60 MPH mileage it goes up quite a bit, temp and traffic impact things a lot, also hills. I get 27.5-32 depending on the above driving around 75 MPH most of the time on cruise and I have a A/T. Usually normal freeway commute with AC is 29MPG. Cool but not cold weather helped MPG by about 2 MPG after the winter. I commute 128 miles 95% freeway everyday. Very consistent MPG regardless.

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Originally Posted by Brian

To the OP, I get very similar MPG in a '10 sedan. 50-60 MPH mileage it goes up quite a bit, temp and traffic impact things a lot, also hills. I get 27.5-32 depending on the above driving around 75 MPH most of the time on cruise and I have a A/T. Usually normal freeway commute with AC is 29MPG. Cool but not cold weather helped MPG by about 2 MPG after the winter. I commute 128 miles 95% freeway everyday. Very consistent MPG regardless.

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Thanks Brian! I appreciate that information. It looks like my mileage is consistent than for that speed with A/C and cruise. I will just have to learn to go slower and I will certainly be waiting for it to cool down so I can dump the A/C...

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Originally Posted by RiderOnTheStorm

Your milage sounds fairly close to mine so I feel a bit better seeing that - thank you! What speeds are you typically driving?

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mostly city, around where I am 45 to 55 mph, last october I took my 2 yr old daughter to San Antonio, from where we live its all highway, a straight shot on the highway for 5 hours at 70-75mph I actually got 37mph with a/c used a little here and there on the drive. a few months ago we (my wife, daughter, and my self) took a 12 hour drive to new orleans in my wifes 09 corolla, the best I could get in the corolla was 33mpg that was at 3am on I-10, so there was no traffic, not using a/c had cruise set at 65mph

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Originally Posted by redrob

Its nothing that I have gone into researching.............its just something that I have heard as well. When I would get a new car it wasnt to save gas so I wouldnt check to see what my MPG was and when I bought this car (to save gas) it was used. I do remember there being some rumors about engine shavings and impurities in the oil for a new engine but I dont know if that affected MPG or if it is even true( again I dont care enough to go do some scientific research) to begin with. BTW do yoou have any info other than your experience that confirms that this "myth" is just that or do you just say this casually?

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I log all my MPG on all of my cars (3) with every fill-up, so I have a continual record of it for the entire life of each vehicle, and I've been doing this for 40 years. I typically will own a car for more than 20 years, as each one is only driven about 5000 miles per year. I've never seen any improvement in MPG in any of my cars as they got older, and most were bought new. (I currently have cars that are an '89, a '99 and the '09 Aveo.)

Since there is no proof that this is anything other than a myth, it deserves to be called that. Also the idea that MPG would increase flies in the face of logic. The only difference between a vehicle when it is new compared to when it is old is the amount of wear it has on it. I don't see any way in which increased wear is going to improve MPG at all.

i think the "myth" started with poor manufacture standards, as cars in the past have been delivered with unseated rings.. it would take 100 miles or so for the to seat, and if seated properly, an oil change and then the "improvement" while running/driving.

But that is ancient history. Even though some manuals say otherwise, most engines are started and rings are seated by the time they leave the factory today.

i myself see improved gas mileage in summer, summer fuel is much better than winter fuel. but also on cooler days, as stated. plus some brands of gas are much better than others for mpg.. so keep that in mind. Although i am not a fanatic like Thyme...

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Originally Posted by petrified.rabbit

i myself see improved gas mileage in summer, summer fuel is much better than winter fuel. but also on cooler days, as stated. plus some brands of gas are much better than others for mpg.. so keep that in mind. Although i am not a fanatic like Thyme...

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Isn't the difference in summer mileage and winter mileage more attributed to temperature? I am not trying to challenge you, especially since you're quite the expert and I'm the small fry here :) But I thought temperature extremes, especially cold plays havoc with mpg.

Also what fuel do use or recommend? I used to use BP prior to buying this car, but since GM recommends "Top Tier" fuels and there is a Shell close to my home, I use that.

i have the best luck with bp and sunoco.

temperature does have a lot to do with mileage. but even when it is warm still but winter fuel is still in the pumps, MY aveo gets 270-280 mile per tank, instead of the 300-320 it gets with similar temperatures and driving when i know it is summer blend.

disclaimer: i loose the same amount of mpg with sheetz and getgo gas (two local popular discount brands), regardless of time of year. we do not have a shell locally, but one is opening, i am interested in seeing the resulting mileage.

My Aveo ran a lot better after 1000 miles. Then again, I also had opened up the airbox and swapped out the rear muffler by then too which not only helped power, but MPG as well.

With my scanner plugged in, I get an "immediate MPG" result of about 47MPG at 70MPH. Thats probably high but for the purpose of this test I was only testing against myself. Turning on my A/C would drop it to 33, this was done over a 17 mile stretch of highway multiple times on multiple days with the same result.

I should also point out I have a hatch so fuel economy takes a big hit at speeds above 70mph

chad
Unique Motorsports - Mostly cars, some info regarding installs, some tech, some around the house upgrades, and a few other random ramblings.

Does anyone know what the plug is called that is on the coolant line that triggers the compressor to come on? My cold air intake was sitting on the plug and it cut come wires :(.

cycling switch?

its the pressure switch.

So I bought a ScanGauge shortly after starting this thread and then drove about ~2000 miles in that time. With all of that said I have been carefully eyeing my "instantaneous" mpg and when I cycle the A/C on I lose about ~3 mpg. Typically this is at highway speeds (usually 65), but it goes from 33.5 to 30 or so. I think this supports what petrified was saying about a 10% performance decrease. Anyone else seeing anything similar?

That is not the case I have a 2006 Aveo Automatic transmission that Gets poor gas mileage when using Air conditioner Especially during A paper route the car only gets 24MPG My mom's new car gets way better than the Aveo.

running a paper route is worse than city driving.

if your getting 24 mpg while doing something worse than city, with the ac on, your doing well..

i usually use my air conditioner, but ive been averaging about 17 mpg. I dont know what's wrong, but i guess ill be rolling the windows down from now on. :mad:

Just FYI:

From the U.S. National Renewable Energy Laboratory:

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Vehicle air conditioning (A/C) systems represent the major auxiliary load on the engines of light-duty passenger vehicles, sport-utility vehicles (SUV), and heavy-duty vehicles and have a dramatic effect on fuel consumption and exhaust emissions in conventional vehicles and hybrid electric vehicles (HEV).

Recent studies (paper is from about 2000) have shown that, during the SC03 drive cycle (simulating city / ex-urban driving average speed of 21.6 miles/h, maximum speed 54.8 miles/h), the average impact of the A/C system over a range of light-duty vehicles was to increase

1) fuel consumption by 28%,
2) carbon monoxide emissions by 71%,
3) nitrogen oxide emissions by 81%, and
4) non-methane hydrocarbons by 30%.

Recent tests on hybrid electric vehicles (i.e., Toyota Prius / Honda Insight) at NREL [2] have shown that HEV fuel economy decreases by 30%-35% when the A/C operates.

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I own a 2005 and a 2008 Aveo 5-speeds both have well over 100,000 miles and both average between 42 and 48 mpg at 70 mph on the highway, but I don't have A/C in them. For some reason they don't start getting really good milleage till they hit 60,000 miles on the odmeter which both of mine did. One thing that is strange, the Aveo get better mileage at 70 mph then 55.
They only thing different is I run the Amsoil oil and oil filter on them since I drive close to 800 miles week and you can go 15,000 on oil change with Amsoil.

A/C and mileage concerns.
I have over 127K on my 2005 Aveo with automatic and it still runs pretty well. I keep meticulous records on ALL my cars. I have gotten as low as 25.2 mpg around town with AC on to 29.6 mpg as the high. Our temps here has been 99 to 112 degrees this last six weeks so I run the AC a lot. My road mileage has been 32.1 to 38.3. I drive on the roads, no interstate, @ 60 to 65 mph. If I would drive 55 to 60 maybe I would get near 40mph. I do feel that the AC might take off some mpg, maybe 2 ? Very happy with my MPG

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Originally Posted by cameraguy

A/C and mileage concerns.
I have over 127K on my 2005 Aveo with automatic and it still runs pretty well. I keep meticulous records on ALL my cars. I have gotten as low as 25.2 mpg around town with AC on to 29.6 mpg as the high. Our temps here has been 99 to 112 degrees this last six weeks so I run the AC a lot. My road mileage has been 32.1 to 38.3. I drive on the roads, no interstate, @ 60 to 65 mph. If I would drive 55 to 60 maybe I would get near 40mph. I do feel that the AC might take off some mpg, maybe 2 ? Very happy with my MPG

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Hi cameraguy,

Thank you for your post. Glad to hear you're still reaping the benefits of great MPG with your Aveo at its current mileage and Aveo still is giving you good service. If you have any further questions or concerns, please post.

Vanessa
GM Customer Service