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# Cold Weather = Lower Gas Mileage?

9 Dec 2013, 11:10 am

Over the weekend I had another experience that might sound familiar to many of you.

Temperatures drop, and so does my mile-per-gallon rate.  I try to keep track of mileage as I drive a nearly 16-year-old small SUV.  In the summer?  It gets 25mpg.  This past week?  Down to near 20mpg.

I was looking at the following site: http://www.metrompg.com/posts/winter-mpg.htm and it lists the miles per gallon of a Honda Civic Hybrid vehicle based on temperatures on the highway, and it’s quite enlightening:

MPH—–AMBIENT-TEMP—–MPG (US)

60————95———-52.98
60————85———-52.62
60————75———-51.16
60————65———-49.12
60————55———-47.22
60————45———-44.67
60————35———-43.05
60————25———-41.54
60————15———-39.41
60————05———-38.09

The coldest MPG is 28% lower than the warmest.

Thanks to www.stacymakescents.com for this picture.

Doing some research, I found a VERY interesting and informative blog by a colleague of mine, Brad Panovich (click here to see his blog site).  I’ll list the main points of his article, and then fill in the gaps in info with some of my own thoughts and some research from other sites.

1. More Idling – Do you keep your car idling to warm up before you drive somewhere?  Do you find yourself sitting in winter traffic jams?  There isn’t much you can do in many cases about either of those, but it helps explain some fuel efficiency loss as you’re burning gas and not traveling.

2. Lower Tire Pressure – As air cools it condenses, so you end up with lower air pressure in your tires.  Here is how Brad of www.wxbrad.com states the air pressure influence: “For every 10° drop in air temperature outside your tires will lose 1% in PSI or inflation. For every 1 PSI that your tires drop in pressure you will lose about 0.4% in Fuel economy. So if your tires are under inflated by just 3 psi your car would go from getting 22 mpg to 21.7 mpg. It adds up over a tank of gas.”

3. Lower Engine Temperatures – This is another one I’ll leave to Brad to explain:  “Your ideal engine temperature is around 150°-195° depending on your make and model. Most modern cars with computerized management systems for the engine will order up more gas in the combustion camber to compensate. More fuel is added to the air/fuel mixture when the engine is cold. ”

4. Higher Oil & Lubricant Viscosity – Engine oil thickens as it cools, and that causes more drag internally in the engine.

5. Higher Electrical Usage – Think of all the devices you use.  Seat heater, rear defroster, etc.

6. Weaker Gasoline Blends – Gasoline companies create blends of gasoline that will burn different in the cold weather, which often result in diminished amounts of energy when you’re actually burning the gas.

7. More Aerodynamic Drag – There are two parts to this.  Cold air condenses, so you have more air particles per cubic inch that are hitting your car in colder weather – thus more drag.  You also might be driving around with snow on your vehicle, thus creating new drag as well.

8. Icy, Wet or Snowy Roads – Do you have a switch for 4wd vs. 2wd?  That would be an easy answer, but if you drive an all wheel drive vehicle and your wheels slip you’ll be using more engine power than you might even realize to compensate and send power to a different wheel.

9. Another interesting piece I found while researching: Rolling resistance.  Basically, your wheel smushes every time a portion reaches the ground, while the part not touching the ground tries to return to its original shape.  Rubber is harder when it’s cold, so it takes more energy to “smush” it.

So there you go!

The best solution?  Warmer weather!

WeatherNation Meteorologist Aaron Shaffer @ashafferWNTV