I bought 12 gallons when we did our change (per Dave F). Used almost all of it, between the gen set and engine. The radiator and surge tank hold the rest
I had a hard time with the funnel I had filling the radiator, so I took some PVC pipe with 90's and 45's and cut to fit to ease pouring the coolant in. Maybe you won't need to do that with the ISL.
Tom, Patty, Hannah "The Big Dog" and Abby Kat, Indianapolis, Indiana 2000 36' FDS 72232 Our Photos
We live out in our old van. Travel all across this land. Drive until the city lights dissolve into a country sky, me and you - hand in hand.