Coolant returning to surge tank continuously

[tree98]

The red has supplemental coolant additives(sca's) added to it to prevent cavitation on the liners. You can use green but you have to add sca's and check the levels periodically.

To change it just drain the entire engine of coolant (take off the lower radiator hose) then to refill it with red, pull a vacuum on the system with a vacuum pump and then pull the new coolant in.

Don't just drain the system and then fill it by pouring the new stuff in without pulling a vacuum. That could result in air pockets you don't want.