On my 15 Anthem, the generator coolant was plain old Prestone coolant. Yellow green in color. Although Chucks suggestion is a logical one, Id rather carry 2 bottles of coolant (actually 3 considering the AH) than drain the radiator of the Onan just to get the same color coolant. My recommendation, look in the coolant tank with a flashlight and see the color. If it is yellow/green, add Prestone.
Gary and Dee, Zowie and Bowie (traveling cat sibs)
2019 Cornerstone 45B, X15-605hp, Imperial, Spartan K3,
2013 Honda CR-V toad, Demco Excali-Bar II,
Demco Baseplate, Demco Toad Light system, 73 de W5FI