I'm looking at a fluid flush for my 2010 Nissan Altima. I want to ask if there are concerns or benefits to using a lower coolant ratio. I travel to Kansas for the holidays, where it's quite a bit colder in the winter. I stay for several days. Also, do you recommend additives for the water flush portion, and for how long to flush with water before adding coolant again? Thanks.
Coolant formulation is just as the terminology suggests. It's not "only" anti-freeze, but a combination of chemical substances which provide optimum heat transfer as well. The ratio recommended for a specific manufacturer's product will cover hot and cold weather equally well, unless otherwise specified on the label.
As you've created two questions in one post, I have answered only the one with which I am familiar. Perhaps a second post to ensure compliance with the rules is in order.