When heater is on engine won't turn off

Yup, it is the only way to produce the heat for the cabin. You can turn down the heat and/or use ECO mode to help things out a bit. Cold temps and hybrids don't mix well but at 43mpg, it still beats most if not all the others out there.

 

Correct. Nothing wrong. About the only thing one can do it reduce the engine running due to heater use is what I mentioned under Better heater management at Why mileage gets worse in winter | PriusChat

 

During warmup, the ICE won't shut off until the coolant temperature reaches a certain threshold. That threshold depends on both throttle mode (ECO vs normal/PWR) and cabin heat (Off / On). That means there is a temperature band where, while sitting at a stop light, I can turn the engine on and off simply by playing with these switches. An engine monitor displaying coolant temperature will make more sense of this.

Yes, it hurts MPG. Welcome to winter! And there are additional factors that hurt winter MPG.

 

Source: Relooking at warm-up | Page 6 | PriusChat

Bob Wilson

 

Since all cars have their fuel mileage affected by Winter weather, be happy that you're still getting better fuel mileage than they are because the Prius has a unique heating system.

 

45 seems low under ideal conditions. How do you accelerate? What speeds are you driving? What's the pressure in your tires? How are you braking? Flooring it from a stop light and jamming on the brakes to stop would probably return that kind of MPG's. There's a slew of issues that may be present that no one here can answer without some feedback from you.

 

The Prius uses the EGR cooling system and a water-jacketed exhaust to heat the coolant faster.
You can see the extra pipes in this video.

 

Check the battery with a voltmeter. Check after the car has been sitting overnight or after a prolonged period of non-use. If the battery is the original, it could very well be weak or failing.

 

I read on a Volt cold weather tip sheet that using the seat heaters instead of the cabin heater to stay warm is more efficient. If you have the seat heaters, give that a shot and see what happens.

 

Seat heaters burn my butt and freeze everything else. I would rather have seat coolers.

I dont know if its just me but my heater works ok when I take it off auto.

 

This is either the first or second time I'd seen that video. I don't think I even knew it existed until now or recently... I was actually at that event where the filming took place, along w/Wayne Gerdes, the Priuschat moderators of the time + 40 or so other Prius fans, mostly Priuschatters.

 

Minor correction, the miniVCI data show the "EGR cooling system" is used at high power settings. During warm-up, it remains closed and this makes sense. The rich mixture during warm-up coming directly from the exhaust manifold would easily "coke up" the EGR heat exchanger.

The miniVCI data also shows a binary signal, "Request Warm-up" that is associated with faster coolant warm-up:

• 2.61 C/min - with "Request Warm-up" OFF
• 9.62 C/min - with "Request Warm-up" ON

Bob Wilson