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As the temperatures slowly warmed into the mid 70s over the past few weeks, I noticed no neglible drop in MPG on my 06 Prius.

Then whammo - summer hits this past Friday - temperatures jump into the high 80s in NJ. I have Auto AC on, inside temperature set at 70 degrees, and watch miserably as my MPG plunges from 54 to 47. I have since taken turned off Auto AC and have the AC set to Medium but I am left wondering: What's a Prius driver to do? Sweat it out? Open windows cause more of a drag on the car harming MPG worse than AC, right? How do those of you in warmer climates balance MPG efficiency with AC use?

Please help! I hate seeing the MPG drop so much...

JP
 

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That depends on whether you prefer getting great gas mileage and being comfortable or getting really great gas mileage and being sweaty. Only you can answer that. Personally, I go for comfort and let the temperature/mileage thing average itself out.
 

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Trust the Auto A/C setting. It will run hard, then throttle back as the temperature hits your setting. Bump it up a degree or two and it will run less. Find the highest setting at which you are comfortable. I usually leave the windows open until I get on the freeway, especially if I am lined up at a metered ramp.
 

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I leave my Auto A/C on year round. Just made a trip to a marina in Maryland (about 180 miles RT) and got 55.4 MPG for the trip. I haven't really noticed much of a difference with the Auto A/C on or off. I experimented during the 1st year I had my 04 and didn't see a difference in MPG that warranted being uncomfortable.
 

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Is California considered a hot climate? 8) I use my AC year round, but set it to the highest temp setting I can where I don't feel like I'm melting. My lifetime MPG is 48.5 MPG. This is actaul and not the computers best guess.
 

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firepa63 said:
I leave my Auto A/C on year round. Just made a trip to a marina in Maryland (about 180 miles RT) and got 55.4 MPG for the trip. I haven't really noticed much of a difference with the Auto A/C on or off. I experimented during the 1st year I had my 04 and didn't see a difference in MPG that warranted being uncomfortable.
Here's the only reason I don't use auto A/C:

When I get into the hot car and start it, the Auto A/C comes on like a full-force gale, trying to immediately cool the interior. Why can't it come on slower, in a more measured fashion? I don't need my 100 degree car to get cool in 10 seconds. I can't imagine the energy required to perform this violent climate change.

Therefore, I prefer to run it manually.
 

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You still have to remove the heat, so whether you do it quickly or over time, you consume energy to do it. Not a lot of savings either way. I usually roll the windows down for a few minutes when I get in if it's real hot. The fan usually slows down after a few miles of driving.
 

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Those of us in hotter climates are "used to it." OF course, summer doesn't hurt so badly when we started our first 90 degree days in late February/ early March! Spouse has a magnum hemi and would rather sweat than waste gas on AC, these days. It depends on individual tolerances and if that car ride takes you to a hot date (use AC) or a cool shower at home (sweat it out). For those of us in the Florida fire zones, the less you draw in that lovely smoke, the better off your interior.
 

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Temparature is an individual sensation. Temperatures making me comfortable are forcing most other passengers to complain and sweat. I usually set my AC at 72 degrees, then further in to the trip I raise it upwards finally reaching 76 as top position, otherwise I start feeling cold, especially when the fuzzy logic starts to emit the air from the dash outlets.

Opening all doors and the trunk to get rid of hot air before turning on the engine (well the hybrid system) is a good idea and makes it easier for the system to cool down the car.

Walter
 

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dgstan said:
Here's the only reason I don't use auto A/C:

When I get into the hot car and start it, the Auto A/C comes on like a full-force gale, trying to immediately cool the interior. Why can't it come on slower, in a more measured fashion? I don't need my 100 degree car to get cool in 10 seconds. I can't imagine the energy required to perform this violent climate change.
Ah, there's the problem: failure of imagination. It runs *most* efficiently at full bore. The total energy used is greater if you manually force it to dribble less-cold air for a longer time. Let the machine do its job.
 

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I have mine set at 74 degrees. I usually open all the windows while I wait for my friend to finish work and meet me in the parking lot. If the temp is milder (under 82 degrees without too much sun) I'll drive wtihout AC. Otherwise it's just too hot and I'll just take the MPG hit.

Keep the car shaded whenever possible so you don't heat the car with radiant solar heat. Mornings are great for me, so are late evenings. Day trips are a killer.

Another trick, if it is just you, put the vents directly on your face/body. Then you can raise the temp and/or lower the fan speed. Just note though, you can't control the compressor speed directly.
 

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Returning from a weekend away, we flew home to realize temps in the 90's with humidity. Boy did that mpg drop. With short jaunts from my home and a very hot car, I'm at 42mpg and dropping every day. (Those first 5 minutes I'm under 25mpg and can't seem to recoup to make a good average.) When the weather cools a bit, I don't mind open windows, but I couldn't stand being without AC in typical Chicago hot weather. P.S. Didn't see many Priuses in Missouri and Nebraska. But heard laments about gas prices for the Yukon my niece drove us around in.
 

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Let's look at some numbers. Say your commute is 20 miles:

20 miles * $3.00/gal / 54 MPG = $1.11
20 miles * $3.00/gal / 47 MPG = $1.27

So you have a choice: sweat for the entire 20 miles or pay the 16 cents
and ride in comfort.
 

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RealAle said:
Let's look at some numbers. Say your commute is 20 miles:

20 miles * $3.00/gal / 54 MPG = $1.11
20 miles * $3.00/gal / 47 MPG = $1.27

So you have a choice: sweat for the entire 20 miles or pay the 16 cents
and ride in comfort.
You forgot drycleaning charges. :wink:
 

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I live in Central NJ, and I don't like hot, muggy weather - I sweat a lot and it's uncomfortable, too. In the summer, I usually keep my A/C in my house set to 74 and sometimes I'll lower it to 72.

But this past weekend was the first time I used my Prius' air conditioner. You're right, it sucks up gas, but I've found I'm comfortable with the Auto AC with the temp set at 75, even when we hit the high 90's with bright sunshine. I feel like it lowered my mileage about 2 MPG, from about 50 to 48 (most of my trips are short trips).
 

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Jeannieb360 said:
I live in Central NJ, and I don't like hot, muggy weather - I sweat a lot and it's uncomfortable, too. In the summer, I usually keep my A/C in my house set to 74 and sometimes I'll lower it to 72.

But this past weekend was the first time I used my Prius' air conditioner. You're right, it sucks up gas, but I've found I'm comfortable with the Auto AC with the temp set at 75, even when we hit the high 90's with bright sunshine. I feel like it lowered my mileage about 2 MPG, from about 50 to 48 (most of my trips are short trips).
That's about the same drop I see. Drive your coworkers crazy by bitching about your drop to 48mpg.
 

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Hep said:
That's about the same drop I see. Drive your coworkers crazy by bitching about your drop to 48mpg.
I do that all the time! :D :D :D

One thing I do when I park in the moring is use a sun shade in the front window along with all 4 windows rolled down about 1 to 2 inches. When I get in my car, it's not too hot inside. This helps keep me from blasting the AC when I first get in. I also roll the windows all the way down till I get to the freeway. Then they go up and the AC goes on! I don't think I'm seeing a 2 MPG dip ... but that may be partially do to the fact that I use the AC all year. A 2 hour workout at the gym each morning is a bad way of keeping the body temp down...
 

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I find once the car is cooled, I can minimize AC while maintaining comfort by setting the system as follows:
AC on
Temp to 78
Fan on medium
Recirc
Vents aimed at my shoulders
This is comfortable but doesn't run the compressor all that much. My gut average is abotu a 2mpg loss, well worth it now that afternoon OAT is around 90 and climbing.
 

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This AC is great its so cold in my car that I have to raise the temp to 72 and its still very cold. Best AC I ever had and the MPG are still ok
Anyone know why its works so good, Does toyota have a better AC system than I'm used too?
 
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