This is I believe to be true, anytime we had a sticky lock cylinder on a customers car at Ford dealership I worked at. We would use Motorcraft penetrating and lock lubricant.There might be some ice in the tumbler. The heated key trick works, but not too hot. I've read lubricants like WD40, Liquid Wrench or oil aren't good for locks. Locks need something like graphite as to not gum up the mechanism.