Toyota Prius Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter #1
Hi all,

With summer just around the corner I was wondering if running the air conditioning effects MPG? I don't think it does since I imagine it runs off the electric motor.

Any ideas.

Thanks!

Daktron
 

·
Registered
Joined
·
2,243 Posts
The MPG hit is nowhere near a belt driven compressor. The electric compressor is variable speed and will adjust to the required load. Just leave the system in Auto AC and adjust the temperature to your comfort. I leave mine in auto year-round with the temperature set to 70-72 degrees.
 

·
Premium Member
Joined
·
887 Posts
A few years ago a service manager said in passing that the wost thing you could do to an air conditioner was not use it. When vehicle air conditioning systems are in use the oil that lubricates the compressor runs throughout the vehicles refrigeration system. A secondary benefit of having the compressor lubrication running through the various hoses and coils in the system is that that same oil that lubricates the compressor also keeps seals and o-rings fresh.

If you choose to not use your air conditioner the refrigeration oil will migrate to the lowest part of the system and seals and o-rings tend to dry up and contract. Once that happens your refrigerant leaks out and then you don't have an air conditioning system until it is recharged.

The reality is that it is concieveable that any savings in fuel you may get at the pump by not using your air conditioning will be offset by the unnecessary expense of a premature recharge or full system rebuild.

Additionally the Prius is a wholeistic vehicle in nearly all of its operations. Battery temperature control is derived from moving cabin air past the battery during its operation. In the winter when the battery is too cold to operate efficiently the vehicle uses cabin heat to warm the battery. In the summer when you enter into a hot vehicle the cooled cabin air is used to reduce the battery temperature to a more optimum level. The vehicle communicates air conditioner panel settings to the vehicle as a whole, both to optimize vehicle performance when using air conditioning resources and in determining the degree to which warmer, or colder, cabin air can be used to regulate battery temperature.

I live in a very hot and dry summer climate, it's not Arizona or New Mexico, but we easily get a handful of low humidity hot summer days in July and August. Easily over 100 degrees. My best mileage statistics always occur during the heat of the summer with air conditioning in use. I don't worry about mpg with a/c because the effect is so minuscule and because the vehicle needs the auto climate system for more than just providing your comfort.
 

·
Registered
Joined
·
289 Posts
firepa63 said:
The MPG hit is nowhere near a belt driven compressor. The electric compressor is variable speed and will adjust to the required load. Just leave the system in Auto AC and adjust the temperature to your comfort. I leave mine in auto year-round with the temperature set to 70-72 degrees.
For me, I found that setting the A/C on 'auto' ran the ICE more and sapped MPG more than setting it manually to 72 and having the fan on the lowest setting, unless it gets really hot then it goes up a few notches as needed. Of course, YMMV...
 

·
Registered
Joined
·
39 Posts
Technical issues aside -- which gives you a bigger "hit" to your MPG's: use of AC (increased ICE requirements) or rolling the window(s) down (distorting the aerodynamic shape of the Prius)?

FWIW I leave the temp control set to Auto year round. I'll take the hit to my fuel economy - I have enough to micromanage in my life already! :lol:
 

·
Registered
Joined
·
140 Posts
diverdoc said:
Technical issues aside -- which gives you a bigger "hit" to your MPG's: use of AC (increased ICE requirements) or rolling the window(s) down (distorting the aerodynamic shape of the Prius)?

FWIW I leave the temp control set to Auto year round. I'll take the hit to my fuel economy - I have enough to micromanage in my life already! :lol:
At highway speeds, you're better off with the AC, unless you can tolerate just two windows down an inch or so. At speeds of less than 40 or so where the aero drag of course is less of a factor, open windows will do better. This according to the Prius MPG Simulator (http://privatenrg.com).
 

·
Registered
Joined
·
3 Posts
I'm the newest of the Newbies (~60 miles on my '08 Prius and counting) and I have to say that I never considered any of this with my '89 Tercel 5-speed, even at 150,000 miles when the clutch finally went up, and always got 50mpg highway, 45mpg mixed and 40 mpg City. Have we made life too complicated or what?

I don't mean to be a downer, but I expect at least as much out of my Prius which costs a hell of a lot more than that Tercel, even taking into consideration the decline of the dollar. I hope in a month I will be a convert. But the Prius was the only vehicle out there that claimed to get 50mpg and though I am severely altering my driving style, I am not yet convinced.

I heard a rumor that Toyota is working on a 75mpg Prius. I wish they would put the effort into a 75mpg Tercel instead.

Tercel Lover Forever
 

·
Registered
Joined
·
13 Posts
I live in Florida so the AC is on all summer long. IMO some people take this MPG a little too serious. I’m not saying getting the most out of your gas is wrong or that I don’t try to do it too but not at the expense of being miserable. (LOL) On that not I am hot blooded as it is. When summer comes around and people go to the beach and out to have fun in the sun I retreat to the comforts of my AC house. I wouldn't survive if terrorist attacked the power grid and my AC didn't work. I went through that in IRAQ... Never again!

Come fall the AC goes off.
 

·
Registered
Joined
·
4 Posts
how much help would a solar trickle charger help to keep the engine from coming on to recharge? is there a way to test this?
 

·
Registered
Joined
·
2,285 Posts
Not nearly enough power to matter.

A news item a month ago talked about Toyota's plan to add optional solar panels to the roof of the new model (2010?) which would run the A/C, but consensus is that they only mean the fan, not the compressor. Same problem--not enough power.
 

·
Registered
Joined
·
99 Posts
I've tried it both ways down here in Florida and A/C costs me roughly 3 - 5 MPG depending on how hot it is. I generally keep my AC set to 77 and auto. I also believe that the sensor is off a bit because 77 feels much more like 72.
 

·
Registered
Joined
·
884 Posts
Earlier in the summer, Arizona had a few weeks of 110+ degree weather, and mileage dropped to 42-44 mpg. Now, that it is cooler (105-108), mileage on our 2002 Prius has gone back up to about 48 mpg, short of the spring and fall highs of mid-50 mpg's. Can't wait for the monsoons to pass.
 

·
Registered
Joined
·
2 Posts
Phoenix said:
Earlier in the summer, Arizona had a few weeks of 110+ degree weather, and mileage dropped to 42-44 mpg. Now, that it is cooler (105-108), mileage on our 2002 Prius has gone back up to about 48 mpg, short of the spring and fall highs of mid-50 mpg's. Can't wait for the monsoons to pass.

I'm interested in this suggestion that tires should be inflated to 42/40 and maybe even higher. Would you know if it's safe our intense summer temps?
 

·
Registered
Joined
·
884 Posts
I had a set of Michelin HydroEdges that that I ran at 44/42 psi for 65,000 miles before replacing them early (still had about 10-15,000 miles left on them). I now have a second set of HyrdoEdges with about 10,000 miles on them that I have run at 46/44 psi since they were new (about a year ago).

In Arizona, the higher pressures (up to 44 psi max rating) make the tires flex less, which generates less internal heat -- So, in my opinion, this is safer. Besides, the higher pressure inproves my mileage about 2 mpg.

It's your personal choice, but there is no way I would run the factory pressures. The tires would wear out prematurely, with severely worn shoulders and lots of tread left in the centers. And, I suspect there would be an increase possibility of tread separation and blowouts.
 
1 - 18 of 18 Posts
Top