some due... you can see the people who dont due to the square tires in the parking lots sometimes...the worst my truck saw last winter was -67. still running df1 and no additives. it takes a little bit to warm up in the morn at those temps but the block heater, battery balnkets, oil pan heater, tranny heater, and t-case heater do their job.....if you remember to plug the damn truck in.....ive done that a couple of times. nothing like the sound of a frozen truck tring to crank.....ouch...maybe this winter ill get some video of some cold starts onto you tube and put the link on here for ya. ill wait till it gets really cold though...at least -30.. the plum of smoke out the pipe at high idle when it starts is amazing.....