Just bought a oem cold weather blanket. Never used one before. At what point do I close up the front air flaps or do I leave closed until I notice temp getting to hot. Has anyone using this noticed a diffarence?

 

I wouldn't cover it up until the outside temp stays below 30.

 

They have a place in real cold climates. I have used them on some of our fire truck than it get below 0-. But you need to watch your engine temp to make sure you don't overheat and adjust by opening the flaps for some air flow.