Hey All
Even though the colder air of winter does make the motor perform better, most complain about lower MPG during the winter.
As I thought about it (I too am getting lower MPG) I was wondering if my snow tires were the cause, I know that actually driving in the snow will affect my MPG (drag/resistance), yet I was wondering why my MPG has been down a little (figuring snow tires on dry pavement wasn't the cause).
Then I had a small DUH moment, because I drive to work before the sun comes up and come home after dusk (mid Oct to mid Mar) my lights are on for all of my commute as is my heater, so I did some quick calculations and SOME guessing.
Head lights draw 55 watts each (low beams) and assuming same 55 watts for high beams, running lights draw 12 watts each (X 4) and the heater (guessing, 2nd speed @ about 25 watts) indicators/LEDs guessing @ 10 watts.
For reference, 746 watts = 1 HP and we know the alternator output can exceeds the wattage demand of the car under normal use. Having said that and not knowing the efficiency of the alternator (lose to belt, fan, heat, converting AC to regulated DC, etc), I'll guess we'll be lucky if it is 40% efficient.
So what I am assuming (and it's a good assumption too) we get 298 watts per true motor HP. With a load of 193 watts (2 low beam bulbs,4 running lights, heater, and indicator/LED lamps) we consume .67 HP regardless if we are going 1 MPH or 100 MPH.
Our G&K Smarts produce 62 HP, but were not demanding that most of the time while driving around, most of the time (cursing) I would be surprised if we draw 20-25% of that potential (12 to 15 HP).
So in conclusion, there is a lot of guessing here but I wasn't looking to produce absolute numbers, just a model that could explain a reduced MPG during winter (other than driving in snow), SSOO
a 5% loss in MPG could be attributed to lights and heater usage.
Just thinking out loud
ASM
Linear Mode
