Temperature and Fuel Economy

[wellswebdesign]

I've seen discussion on here lately about colder temperatures affecting fuel economy. I just wanted to throw in my two cents worth.

The setup: I've got a ScanGauge E that shows exact coolant temp. I live in Central Ohio, where it's been about 10-15 degrees F. I have an engine block heater that I use whenever I can (unrelated to this post, I just love my block heater is all ).

The observation: With the cabin temp set to 68 to 70, and on auto, it eventually ramps up the fan pretty fast. If I leave it on auto, the fan speed stays high, and my coolant temp wont get up to 195F. If it's cold enough, the cabin fan blowing through the heater core pulls enough heat out of the coolant to prevent the engine from reaching full temp.

It would seem to me that an engine not operating at its' optimal temperature, would use more fuel. Might be worth bundling up a little more, turning off auto temp, and lowering the cabin fan speed. Thoughts?