[bestclimb]

My commute was 18 miles or so. Mornings I used a block heater 65+ mpg on the drive to work was easily attainable. Mornings I did not use the block heater 55 was a struggle. The mile out of my neighborhood would see at least a 10mpg drop if I did not use the heater. I did this several times. I realize the plural of anecdote is not data but it certainly convinced me. If you run the block heater on a timer the hit to the electric bill is not much (if you run it all night...well stupid hurts)

Additionally I would have hot air coming from the vents before the mile in the neighborhood was up (20mpg speed limit) With out the block heater I would have warm air about a mile or so after I hit the 55mph road. So on the comfort (and safety as I could keep the window defrosted) the block heater is totally worth it. The fuel savings is a nice bonus)