Some cold weather tips for better mpg.
I've not found much that works for maintaining summer mpg while using the heater. It appears though that the heater fan, over time, puts an energy drain on the battery. So what I've been doing is manually, frequently turning the heat on and off. I'll turn the heat off when I have high driving need for battery power, and turn heat on when low driving need, or downhill battery charging situations. My comfort is worth paying a small mpg decrease.
Another idea which doesn't seem to do much, has been to turn the heater temperature knob to its lowest setting when engine is cold. This will cut/reduce the amount of radiator fluid diverted from the cooling system to run over the engine toward the heater fan. The idea here is to prevent the cold/cool radiator fluid from slowing the engines' warming-up process. When doing this I'll turn the heater temperature knob to its highest setting once the engine cold light goes out
Moviemike, I appreciate your many tips and follow many of them on getting best mileage. Your stats show you are doing something right! Since your post on managing the heater settings I have been experimenting and offer the following gen 3 specific observations-
I don't think cabin heat is generated through electrical resistance, so it's not the heater fan itself that impacts negatively gen 3 mileage, especially at lower fan RPM settings where a fan draws minimal power- instead it is the demand for heat itself that negatively affects mileage in certain situations. I have noticed, for example, that even if the engine is warmed up, but the cabin is not (following your advice to warm the engine first) the very act of then switching on the heat or turning up the cabin temperature will cause the engine to start running continuously (until cabin heater temperature set demand is satisfied). By turning on the heat in this situation this also means EV mode becomes not available, even when coasting, simply because the engine can now be running solely based on the temperature DEMAND to warm the cabin.
I think this different than gen 2 where the warmed engine was always engaged and therefore had hot water circulating 100% of the time and always available for the cabin heater demands, except when both the car and engine was stopped. Gen 3 does not have the engine running continuously. I try to maximize mileage by running in EV mode (engine not running) when practical and running the engine no more than necessary (again, following your tip). I think this indicates a different approach than what we did with gen 2 with respect to cabin heater management when we want maximum mileage.
I suggest if one is going to manage the cabin heat with trying to maximize mileage, the time to turn on cabin heat in a gen 3 would be 1) after the engine is warmed up from a cold start 2) turning on the heat when the engine is already running to power the car anyway; i.e; when the car has power needs that exceed what's available in EV mode one would be benefiting from getting "free" heat, since an already running warmed engine has to shed surplus heat anyway. This might mean, for example, turning on the cabin heat when ASCENDING a hill, NOT on when descending, at least until the cabin is warmed to the set temperature.
I'm far from an expert, but maybe this post will make others consider this approach or comment otherwise if offering a different theory.