Engine slower to reach optimal operating condition when it's cold.
Dear Car Talk: I have a 2016 Honda Civic. I was delighted to find that my gas mileage was recording at an impressive 41.4 mpg through the spring and summer months.
However, come October, at about the time gas stations switched to winter blend, I watched helplessly as my reading quickly fell to 40.3 mpg and stayed there until the warm weather returned.
I am pushing 70 years of age, my driving habits did not change over the winter, and my driving destinations were the same. The car has less than 8,000 miles logged so far, and continues to perform beautifully.
Am I wrong to blame the difference between summer and winter fuel formulations for this sudden drop in mileage? — Donald
A: Yes. You are wrong, Donald.
And, by the way, I’m sure all of our readers getting 14 mpg in their Dodge Durangos are feeling your pain over that temporary plunge to just over 40 mpg.
The blame for your precipitous drop in mileage goes to winter itself. When the air temperature is lower, it takes an engine longer to reach its operating temperature.
And it’s not until it reaches that operating temperature that it burns its fuel most efficiently.
So more of your driving in the winter is taking place when the engine is running at suboptimal temperature.
For some people, winter mileage also goes down because they take additional short trips they wouldn’t take in warmer weather.
For instance, while you might walk two blocks in the summer to pick up a bottle of brake fluid-flavored Kambucha, when it’s 4 degrees out, you say, “I’m driving!”
So mileage is like your wardrobe, Donald. You just accept that you have one for summer, and a different one for winter.
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