Well you must be wrong in your assumption of what Zinc is used for and my reason for this is when I hauled nothing but motor oil to Natural Gas facilities the main difference in most of the oils I hauled was the amount of Zinc in the formula. These engines never shut off, if possible they ran 24/7 some of these engines had run continuously for several years after overhauls. What I was told about the extra Zinc was mainly for valve life. Keep in mind these were engines that sometimes were made as far back as the 1920's and some were brand new. So I'm sure they are not worried about the cold start up.