Does anyone have any recommendations for the heat settings to get maximum heat as well as maximum gas mileage with a 2005 Toyota Prius your understanding is the heat comes through the air conditioning?

Answer 1

Hot engine coolant is distributed into the heater core of your vehicle when the heater is on. You can make that coolant hotter by changing out the thermostat for one with a higher temperature setting. That should help out with the maximum heat request. As far as the maximum gas mileage request is concerned: on several vehicles there are heater settings that also run the air conditioning compressor. The idea is that sometimes you might want the air to be "dried" when it comes into the vehicle. Many auto manufacturers turn on the AC compressor when the defroster is on so that the air going across the window has less moisture in it. That way the moisture on the windshield will evaporate. If your vehicle has a push button to turn on the AC compressor, just don't push it. That's the part that takes a fair amount of energy to run. While both heat and AC share some of the same air ducting, AC does NOT have to be on while the heat is on. While the above comment is true, note that on the Prius, when you have the heater on and the temperature is lower in the car than the thermostat setting, it might cause the gas engine to run in order to heat the engine coolant which supplies the heat. That being said, there is no way to use the heater on a Toyota Prius and get the same mileage as you would without using the heater because it's going to cause the gas engine to run more than it would it you didn't need the heat. I live in North Carolina and we use the A/C far more than the heat. The a/c can run completely off electrical power without the gas engine and while having the a/c on will drain down the batteries faster than having it off, the gas engine will only come on when necessary to charge the batteries or when you need acceleration or when the car reaches 25 or so mph. But with heater, the gas engine must run pretty much constantly to keep the engine coolant hot enough to generate the heat needed in the cabin in very cold weather. If you live in a milder climate and just need a little heat, I would suggest only turning on the heater when you're already driving the car above 25 mph. The gas engine would be running then anyway. About 10 seconds before you are going to stop in traffic, shut off the heat. This will keep the gas engine from running while you're at stoplights. As I said, this works fine if you're not in a very cold environment, but if I lived up north and it was very cold outside, my gas mileage would just suffer because of the heater.