A sleeping bag that is stored compressed loses it's insulation properties: https://www.rei.com/learn/expert-advice/how-to-store-a-sleeping-bag.html https://www.

A sleeping bag that is stored compressed loses it's insulation properties: https://www.rei.com/learn/expert-advice/how-to-store-a-sleeping-bag.html https://www.rei.com/learn/expert-advice/how-to-store-a-sleep... I keep a Harbor Freight moving blanket in my trunk. It's thick for insulation, and also cheap in case you need to protect your seats after a muddy activity. I also wouldn't feel torn up about laying it down on ice if I need some traction.