If you use green ethylene glycol in a system that was designed for Dexcool, you're asking for trouble, and you'll get it, guaranteed! It creates expensive ongoing problems that will continue to cause problems until you completely flush ALL of the green coolant out and replace it with Dexcool. Always use the coolant the engine was designed to use. Here is a great article that explains why NOT to change over from Dexcool to the Green ethylene glycol coolant.
http://free-auto-repair-advice.blogs...pens-when.html
Dexcool will sludge up if the cooling system is not maintained correctly. The system should be completely flushed and then filled with a 50/50 mixture new Dexcool, every 5 years or 100,000 miles. Dexcool will turn to a brown mud if even a small amount of green ethylene glycol is added by mistake. The radiator cap can also clog up and not regulate the pressure correctly. Cheap insurance just to replace it.