My suggestion is...........DO NOT MIX ANYTHING WITH THE DEXCOOL UNLESS IT SPECIFICALLY STATES IT IS DEXCOOL.
There is a reason mechanics call Dexcool antifreeze Dexsludge for a reason. Mixing universal with Dexcool antifreeze will almost guarantee the mixture will gel and sludge in your cooling system. Look for DexCool antifreeze ONLY!!!
Why are the two types incompatible?
Most automotive antifreeze/cooling systems in this country use ethylene glycol as the main component in their coolant. Because ethylene glycol is naturally corrosive, however, coolant manufacturers have long used inorganic salts such as borate, phosphate, silicate and other chemicals to prevent automotive cooling systems from rusting and corroding. Most automakers recommend these coolants be changed every three years or 36,000 miles.
In 1996, GM began switching its vehicle fleet to Dex-Cool, an antifreeze/coolant that uses carboxylate or organic acid technology (OAT) as its main corrosion inhibitor compound, instead of inorganic salts. Dex-Cool is a registered trademark of GM, for coolant that meets GM specification 6277M. Currently, ChevronTexaco and Prestone are the only two suppliers of Dex-Cool coolant.
The best answer, of course, is to completely flush the DexCool antifreeze from your system and refill with the green universal-type of antifreeze. But you have to make sure you do a COMPLETE cleaning and flush of your system....leave no traces of the DexCool in your system. Drain the system, refill with water, use the Prestone heavy duty radiator flush, drain, refill with water, drain, then refill with universal. You'll be glad you did.
BTW..........just Google DexCool sludge.