I know there may be an article somewhere or maybe even a thread where coolant was discussed in detail, but for the newer folks to POG who have not had the advantage of the discussion on coolant the simple version is if the coolant lists that it meets the Detroit Diesel specification it is acceptable for use. That coolant should be changed every two years and between changes it should be maintained by the use of conditioning filters which are changed every six months. Those filters meter additives (SCAs) into the coolant to maintain the proper chemistry.
As an alternative, the use of coolant meeting the EC-1 spec, an extended life coolant may be used. The two types of coolant are not compatible, and if EC-1 coolant is to be used, the entire cooling system must be flushed and free of the Detroit spec coolant. The EC-1 coolant is to use a blank cartridge instead of one that adds SCAs, and no coolant except EC-1 spec coolant is to be added to the system.
The EC-1 spec coolant was developed by Caterpillar as an alternative to 2 year coolant changes, and its life is typically expressed as 6 years or 600,000 miles, whichever comes first. Brian is our resident coolant expert having arranged the seminar at Spearfish.