For a street car fresh coolant, what ever is on sale is all that's needed. Check all cooling items are functioning as they should. High volume water pump, fan shroud, hoses, etc. I run a plate system eliminating the t-stat. you can get a pack of 4- hole sizes from 1/2. 5/8. 3/4. 1 inch we don't freeze too often so it works great with performance motors that need heat regulation. You change the hole size to fit your application... Works wonderful !