starting fluid, very detrimental?

It works. But sadly I have seen the damage it causes first hand. Swollen piston skirts, blown out piston tops, the list goes on. Old diesels would actually become addicted to it and only start on it. The top rings take the most abuse. If you have to use it… use it cautiously. Better off draining coolant if you are that worried. Can’t freeze if it’s not there.