A somewhat nerdy point - the drop in MPG you experience is not as consequential as it appears to be. Suppose your car goes from 40 mpg to 30 when you turn the heat on. You'll be using an additional 0.0083 gal/mile for heat.
If you have a less-efficient car to start with, and you go (say) from 20 mpg to 17 mpg when you turn on the heater, that's using 0.0088 gal/mile for heat. So the cost of heat is higher in the less efficient car, even though the difference in MPG appears to be lower. MPG is a very counter-intuitive measure of fuel efficiency!
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Date: 2010-12-08 05:48 pm (UTC)If you have a less-efficient car to start with, and you go (say) from 20 mpg to 17 mpg when you turn on the heater, that's using 0.0088 gal/mile for heat. So the cost of heat is higher in the less efficient car, even though the difference in MPG appears to be lower. MPG is a very counter-intuitive measure of fuel efficiency!