T-Keith, I'm confused by your use of the term "true DEXCOOL". Any brand antifreeze that is licensed to display the "GM DEX-COOL Approved" logo
is a true DEX-COOL as far as GM is concerned. (It's their trademark, so they oughta know...) There may be minor variations in corrosion inhibitor chemistry across producers, but they all have to be intercompatible, and organic acid technology in order to pass GM's muster to be licensed. I suppose the case could be made that the "Mr. Goodwrench" DEX-COOL extended life antifreeze/coolant concentrate at GM dealership parts counters could be properly defined as the "true DEXCOOL", but, it
is made for GM by Havoline and reputed to be the very same forumula as the Havoline brand DEX-COOL available through regular retail channels. Whatever the case is for so-called "DEXCOOL sludge", I'm not convinced it's a fault of the DEX-COOL technology - regardless of brand. I've run Havoline-made DEX-COOL in both a 2000 Cavalier (which still has its factory fill) and a '96 Accord with no sludging in either - and I've monitored carefully in each case, so it's not a universal "problem" that could be layed at the feet of Havoline. I'd bank more on some infamous GM gasket problems* allowing air intrusion that have been discussed at length on this site. No antifreeze, and that includes Zerex G-05, can protect when the integrity of the cooling system sealing is compromised. In any event I just put my money where my mouth is: I drained, fully flushed as I described, and installed the new WalMart extended life yellowish, "lime-green" brew in my 2003 Sonata V6 one week ago. (just what the world needed - a highly toxic, sweet-tasting liquid that looks to kids like lime Cool-Aid!) So, time'll tell! The deeper green factory-fill drained ever so slightly hazy after a bit less than 2 years' use (though it was 25 months since the build date on the door jam). That mild haziness leads me to believe that Hyundai's factory fill was not an extended life type antifreeze/coolant. (When I drained the Accord's factory fill coolant, it drained absolutely haze-free and clear - just the green tint of the dye Honda antifreeze/coolant used at the time. This was a good thing because I misread the maintenance interval in my owner's manual. It called for three years, and I waited until into the fifth year...
That Honda stuff had to have been something other than the conventional nitrated, borated, phosphated, hydrated-silicates green-snot-of-death for me to duck a bullet that easily!)
*certain "V" type pushrod engines of GM manufacture seem to be prone to intake manifold gasket and/or cylinder head gasket failures after 60,000 miles or so. Your 3.8L V6 is among those, so monitor your coolant level very frequently and carefully. There were also some issues with radiator caps supplied on GM cars a few years back. Might wanna check with your dealer if yours is one of the suspect ones and replace it if so.