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Old 11-18-2012, 10:22 AM   #2362
stevehnm
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Member#: 329526
Join Date: Aug 2012
Chapter/Region: SWIC
Location: Ground Control
Vehicle:
2013 Impreza Spt cvt
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There are actually several factors why fuel economy suffers in the winter. The biggest, depending on your driving style, is that cold air is just more dense than warm air. That means several things are happening. For one, you are pushing more air - up to 10% more. Another reason is that as a certain volume of air comes into the engine, in the winter that has more mass so there is more fuel put in to compensate. Then, fluids are more viscous (thicker), which increases the power drag - things like transmissions and differentials that don't have cooling "systems" are more of a drag. Tires have less pressure so there is more rolling resistance.

The other reason, which may be major depending on your driving habits, is that people tend to warm their cars up more in the wintertime and take more shorter trips instead of walking or riding a bike, and it does take longer for all of the engine to warm up to optimum temperature in the winter (even though the gauge may say it's already warm).

So, the answer is: It depends...
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