The PO of my car said the Tstat was bad, and its never up to temp unless its really hot out, so m replacing it. I also want to do a coolant flush or change, i'm not sure of the life of my coolant so it should be replaced, how much do i need to buy? I'm going with Zerex G-05 not Benz i have been told its the same stuff. And i found that its half the price in my neck of the woods.

My questions are:

How much coolant should i have on hand when doing the flush? and should i follow the instructions on diesel giant and do a citrus flush with shout gel, etc?

BTW i have a 1987 300SDL