Gas mileage down in winter?

[Jond63]

"Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2)."

I never thought about this effecting gas mileage -- I got the Bridestones for the stiffer sidewalls, but those same sidewalls probably cut down my mileage for this very reason! Hmmm...

 

[DrWebster]

"Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2)."

I never thought about this effecting gas mileage -- I got the Bridestones for the stiffer sidewalls, but those same sidewalls probably cut down my mileage for this very reason! Hmmm...

Well, the way I see it, a stiffer sidewall should actually help mileage -- it would make it harder for your tires to deform, meaning less energy is lost by the rubber flexing. It's the same reason why hypermilers pump up their tires to 50+ psi.

When it comes to temperatures though, colder is not better as it causes the rubber to stiffen. While a stiff sidewall would be good, a stiff contact patch would not as energy is lost from the rubber flexing. The same principle holds true as to why all-season tires do worse in snow than snow tires. Snow tires are made with a rubber compound that's softer at cold temperatures, so it flexes more easily and thus gives you better traction.