Living in the Siberia of the Midwest, I have never had an issue with my 2016 ED or 2020 ED (though the new one has not gone through a full winter) and 7-15 days straight of 10 to 40 degree below zero weather. I do have the winter covers and have it on both trucks. I would not drive with out it as for me it helps in 2 things, it prevents snow from packing it in the front grill while driving in snow, it keeps the engine warmer both when driving and for a bit after you shut the engine down. Warm ups are faster, which is better for the engine, having driven Diesels for many years I am a fan of the covers, I see it as cheap insurance in nasty weather. I know the active grills will provide some aspect of heat retention but I am not as confident in them as a good cover, if we did not experience long spells of very cold weather may not be as big of an issue. As we are getting 8-10 inches of snow once again today, I'll get to have fun with the 4 wheel drive on the freeway