Winter Gas Causing Drop in MPG?

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Originally Posted by captainm27

I know every car suffers MPG drops in the winter. But why is that? Is it because of the winter blend type of fuel being used? Or does an engine use more gas to stay warmer during the coler months? I drive my Yaris the same gentle way I do in the winter as I do during the warm spring days (with the exception of snow storms, etc.) I never see my RPM's going so much higher to suggest using more fuel. Does the engine use more fuel, even though it is keeping the RPM's at the same levels? Or is RPM just not a good indicator of how much gas is being used?

Everything needs to warm up. Oil, grease, water, and the passengers. All that heat plus wipers and defrosters use up extra fuel. The DEF mode for the HVAC runs the air conditioner, too. The snow on the road offers a tremendeous drag that needs to be overcome.
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