Electric Element in Heater
In the thread "Interesting Mirage Quirks", 3plane wrote about the electric heating elements in the car heater. I recall that he said that they provide quicker heat to the car interior and faster engine warm-up. This is a very nice feature. I set my heater to "auto", turn the a/c off, set the temperature I want, and set the "mode" to the vent locations I want. From a cold start, the engine is warm enough to provide heat after 1 km, and the heater fan comes on at a medium speed.
On my typical 8 km morning trip, I was averaging about 5.0 l/100km during the summer but it now averages about 5.5 l/00km. I tried driving the same route with the heater totally turned off. i.e I pressed the "off" button. My fuel consumption went back down to 5.0 l/100km showing that the extra heat is not free. (I have done this a few times and the results are repeatable.) I think the extra comfort is worth the extra 0.04 litres of fuel on the trip!