What's the best settings for AC for better MPG in winter?

Winter is a mileage killer. Cold weather increases rolling resistance, aerodynamic resistance, and forces the engine to make more heat.

The best AC setting for winter mileage is cold. Turn down the temperature to avoid taking heat from the engine.

Tom

 

Geez! Just set it wherever makes you the most comfortable.
Do not try to over-think the Prius - it is just a means of transportation, not a way of life.

 

I would put it on Auto and set the temp to the coldest you still feel comfortable.

 

Amen.

 

Set the temp to 68 - 70 and make sure the "A/C" button is turned off. You don't need to run the A/C condenser unit for warm air. What I normally do when I first start out on a cold morning is switch the system OFF and turn on my heated seat. Once the engine warms up, I then set it on AUTO with a 66 or 68 degree temp setting.

 

MAX HOT with auto off is what has worked best for me.

ECO mode is also a big plus, since that reduces the engine-on threshold.

I start driving with the fan off, then I just keep my eye on the coolant temperature displayed on the ScanGauge. Once hot, you can be surprisingly generous with the fan... and know exactly when the engine is about to start back up. Toasty warm for me. I don't care for driving with gloves.
.

 

automatic mode - temperature setting 75 - air conditioning off - don't touch again 'til summer

 

On the subject of temp vs fan, they are not interchangeable. The fan should be set at the lowest level which accomplishes the desired air mixing. Thus it depends on the number of passengers, whether there is any condensation or frost on the windows, temperature difference, and so on. Remember that faster air directly on your skin will cool to some extent. Heat should be kept off until the engine has heated up, and then set to the desired temperature. I believe the Prius works the same way as a home thermostat, in other words it will try to bring the temperature up to the set point as well as possible, and then turn off until it cools off a bit. So, turning the heat to 90 will not warm the car up to 68 faster than setting it at 68.

 

i keep mine at max cold and fan off. i only use defrost as needed. plenty of gortex, gerry.

 

To elaborate on the above, the OP might want to look at my section on heater management at http://priuschat.com/forums/gen-iii...mileage-gets-worse-in-winter.html#post1411488.

Yep, having a SG is super helpful since you can monitor he coolant temp and know when the HVAC fan might need to shut off to prevent the ICE from running to provide cabin heat. Also, it gives you a reliable ICE on/off indicator. It can be hard to tell if it's on/off while moving.

I doubt that'd give the best mileage. I almost NEVER use auto because I don't know what it's doing (whether it's running the AC compressor when I don't want it, whether it's causing the ICE to run to provide cabin heat, etc.).

 

I would use Auto and set it at a comfortable temperature, but that's unrelated to your question. You asked what is best for mileage. In that case set it at a low temperature and a low fan speed. Turning the fan off completely will save a tiny bit more fuel.

Tom

 

This will be our first winter with a Prius.

Our habit has been to wear a coat / gloves / hat while driving, anytime the temps are below -5F.

Every vehicle has it's own delay from when you first start it, until heat finally starts coming out.

Sometimes we carry spray-bottles with anti-freeze to help clear the inside of the windshield and side windows. Sometimes we have used plug-in 12VDC heaters to blow warm air on the windshield to help get it defrosted, until the vehicle's defrost finally kicks in.

I would imagine that driving a Prius will be about the same process.

We have cracked windshields before, so everyone should be reminded to take it easy when applying heat to a windshield. When heat finally comes out the defrost only use 50% heat setting and never the full 100% setting. You need to slowly warm the windshield, so it warms evenly and does not crack.

 

the thing is, if you're gonna go with low temp, you really don't want it blowing on you.