Optimal temperature for fuel economy?

<div class='quotetop'>QUOTE(efusco @ Oct 18 2007, 02:57 PM) [snapback]527403[/snapback]</div>

At 80 I start to risk spontaneous human combustion. I'm a northern boy, so mileage be darned if the weather gets that hot. I like it in the sixties, although mid to high seventies are better for the ICE.

Tom

 

<div class='quotetop'>QUOTE(pyccku @ Oct 18 2007, 03:40 PM) [snapback]527426[/snapback]</div>

Drops like a rock. It really sucks. <_<

Tom

 

to me it seems that if the outside temp is approx 65 - 70 my FE skyrockets. So far this month I have stayed in the 60 - 65 MPG area. (by the way I drive normal with no pulse and glide) My graphs have been staying pretty much at the 75 MPG straight across. It almost makes me wish I had more than the 20 mile commute each way to work... LOL

 

<div class='quotetop'>QUOTE(efusco @ Oct 18 2007, 01:57 PM) [snapback]527403[/snapback]</div>

Just my two cents here. It seems to be just assumed, that when we Arizonan's complain obout our poor mileage in summer its related to running the AC. I'm sure part of it is. I don't think the AC is whole story tho and you almost have to live in a hot hot climate like we do and have experienced it to understand. When its really hot out, the car runs poorly. AC or not. I had the same experience with my MPG going from 50's to 44-46 during the hottest months. But even if you don't run your AC, the car is sluggish and loud. If you have to gas even a little it kind of roars. Its just not a happy car in the heat. I'm still running my AC now, but the MPG is back up and the car is quite zippy, like when I bought it back in January, when the weather was still nice. Its my first year with the Prius, so now I know, especially after reading a post from another Arizonian that this is what to expect. In the cooler months I have a fairly zippy car with excellent MPG, in the hot months I have a sluggish car that always sounds like its struggling and the MPG is nothing close to what was advertised.

 

Hi Atwork,

But that is what happens to the Prius when the battery level gets low. Can it be a coincedence that the A/C will drop the battery into the purple SOC in about 10 minutes at MAX cool in slow traffic ?

Then again, a hot battery is a battery that is going to tell the hybrid computer you can only have 1/3 the amps I normally can give. Even at 6 to 8 bars SOC. Which is similar to what happens to the Prius at 15 degrees F or lower. Only at 15 F, the rolling fricition and air drag are allot more!

So, if you can insulate your car it might be a good idea. Because it will keep the battery cooler.

 

My best tanks have been at 60-77 degrees .

 

<div class='quotetop'>QUOTE(donee @ Oct 23 2007, 06:50 PM) [snapback]529474[/snapback]</div>

Hmm, I've never run my AC at max. And I've only seen my battery at purple twice since I've owned the car, but I'll have to watch and see if there is a correlation between the low battery and the loud, sluggish feel of the car in the future. I just thought that when the battery was running low, the car compensated and I would never know the difference, wasn't prepared for performance to suffer the way it does. It isn't happening right now tho, now its just like it was when I bought it, quiet and pretty zippy, enjoyable to drive. It seems to me, the Prius is very sensitive to the outside temps, I've read about cold weather problems, I think hot weather problems are less talked about, but they're definately there. Seems the Prius prefers temps of 70-85 ish for the best mileage. I could be completely wrong, but that's what I've observed with mine. Still love the car.

 

<div class='quotetop'>QUOTE(pyccku @ Oct 18 2007, 12:10 PM) [snapback]527381[/snapback]</div>

It dropped down to freezing a couple weeks ago for the first time since I bought the Prius, right after I filled it up. I was getting less than 50mpg and was bummed. We've been back up to 45-75 lately and mpg is going back up. I don't know if there is an actual mpg dropoff around 45 degrees, its probably a continuous decrease in efficiency. There are many highly complicated mpg graphs posted around PC that will tell.

 

Hi All,

While you can more easily tell that the Prius is sensitive to temperature with the MFD, that is not to say that its that much different from other cars. In my SL2, I would AC pulse and glide on the highway. As traffic slowed, I would turn on the AC, then as it accellerated turned it off. Of course, with the AC on and accellerating, the time to accelllerate was allot worse, and used allot more gas. And using the AC as a coasting brake, helped the economy. Fuel economy, even with this technique dropped 7 percent below the best mileage days. I just did not realise it till the end of the week when I pumped in an extra gallon of gas.

Having to run the AC all the time in the SL2 , if I was in Phoenix in June/July, I would probably notice that the SL2 was kinda slow and sluggish these months too. A hot engine has to idle higher, and use the cooling fans. All are extra load on a standard car egine, besides the AC load. The Prius just turns the engine off and saves cooling load.

The Prius AC unit improves the situation, but the battery is still effected by temperaturre. And being stuck in traffic for a long time , even with the AC on a relatively high temperature setting, is going to run down the battery. Its a matter of degree.

Probably the best thing to do in Phoenix, if one has to park in an exposed parking lot, is to get some kinda reflective (like Reflectix material) car cover to put over the top half of the car.

 

For what it is worth, I live in NJ in the northwestern part where I am going up and down hills. Though my mix is about 50-50 (highway-in town), I am able to achieve an average MPG in the hotter weather of about 43 mpg. In the winter (past 1 with my '06), my average drops to about 38-39. It is still so much better than my previous Subaru. By the way, I have also noticed that the winter aditives in the gas also contribute to a drop in MPG. I guess the gas has less BTU's. Oh, I almost forgot, I use only regular grade of the cheepest gas I can find.