I am very interested to hear discussion and techniques people use in different climates to get comfortable while minimizing gasoline use.

I tend to set the cabin temperature, and let the car do it's thing; my wife picks either 'max cold' or 'max hot' depending, and then varies the flow rate for comfort. I suspect this is a poor way of using the AC, but would appreciate advice and explanations from the experts.

 

Hi EricGo:

___I am sure you can imagine what I go through to maximize the FE of my own so let us move away from the extreme discussions.

___If its extremely hot, run the A/C at a temp high enough to keep your ICE’s FE from being bled dry (set your Auto-climate at 80 + on a 90 degree day as an example) and in the winter, 60 degrees F so the heat isn’t being sucked from your ICE either. Light clothing and a cool drink will make 80 degrees F a piece of cake. A bucket of ice will make 80 downright cold Running the vent fan at MAX w/out A/C is my usual and again, run it as you feel comfortable.

___And on to the extreme’s. Look up Hot_Georgia_2004’s and my own discussions from earlier last year on the subject. It works but there is always a price to pay to save a few gallons of fuel …

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net

 

Setting Max Cold or Max Heat will get you where you want to be temp-wise, but it's not the most efficient way to use your system. I'm betting that you've never had a car with automatic climate control. It does take some getting used to, but you have to remember it is like setting the thermostat in your house. You may not get the immediate satisfaction of cool air blowing on your face, but in the long run you won't be readjusting the temp setting continuously.

Certainly you are losing mileage any time you are running the A/C or causing the ICE to run to heat the cabin, but just take it in stride. You're still getting better fuel economy than 99% of all of the vehicles out there. If you're trying to prove a point on how many miles you can squeeze out of a gallon, then shut down the HVAC system and sweat or shiver for the next 500 miles. My suggestion is to set it and forget it.

If you must, there are a few pieces of trivia and tricks to keep in mind.

Trivia #1 - Your Prius will run the ICE and burn fuel at a stoplight just to keep your toes warm. Trick: On cold days, resist popping on the heat until after you are traveling at a speed that requires the ICE to be running. If you come into slow traffic or stop-n-go traffic turn off Auto A/C so the ICE will shutdown at stoplights and slow speeds.

Trivia #2 - The Prius has NO vent mode. It just isn't there, and even if you're not using the air conditioner, the Prius loves to enable it. Even if you're just trying to vent some fresh air, the Prius almost demands to be either heating or cooling the air, even if only a couple degrees. The closest you can get to vent mode is manually turning off the A/C button and setting the temp to Max Cold. Pay attention as you make your settings as the Prius will continue to try to auto-select the vents and fan speed even when Auto A/C is off.

Trivia #3 - It's easier to maintain a temp than to change it. Just like the brains behind the cruise control is pretty darn fuel efficient, so they are for the Auto A/C settings. Of course we can always wreck it by wanting to travel 90MPH or setting the cabin temp to 65 when it's 105 and humid outside. Pick temperatures that are comfortable, not perfect if you are interested in maximizing your fuel efficiency. If it's 105 and humid outside, you're really going to reel from the heat if you have the cabin down at 65 (if even possible).

Good luck and enjoy your car. After all, at least you aren't driving a H2 towing your closest buddies broken down H2.

 

I couldn't agree more with PrimeRisk. His points are very clear and well put.

However, here is my philosophy taken from Ron Popiel. "Set it and forget it". Pic a temp you want to run at during the winter, say 65 and a temp you want to run at during the summer, say 75 or 80 and don't mess with the system. If you need to defrost, use it, but beyond that the car tends to take care of itself. The logic the vehicle uses for cruise and also auto climate is amazing. The car was built to be no compromises with regard to passenger comfort and also to maximize efficiency, let it decide what to do.

 

A general rule of thumb, if you want the Prius I to do as little as possible, yet still maintain some airflow is to use Auto fan speed mode and then adjust the temp to the point where the fan is at it's lowest speed, that is when the selected temperature matches the cabin temp, so it is doing it's neutral mode at that point, neither heating or cooling, now you can manually adjust the air flow but that temperature is not always so comfortable, so one must always balance that with the fact that driving may require some comfort. Unfortunately the Prius likes to keep the ICE running while the fan is blowing, often you can "manually" start and stop the ICE by turning the fan on and off.

 

I find that I don't use the air/heat much at all in my car. I tend to just lower the windows for comfortable airflow. Having said that, here in the Quads it has been 80s - 90s for temps lately with humidty near the same. I have set the auto a/c for 78 F and left it alone. So far, I haven't noticed an impact on fuel economy for this tank. In the winter, I just set it at 65, and let it go.