BlueOvalFitter, was(were) the jug(s) sealed with a foil/plastic membrane? Something doesn't smell right, here - in more ways than one. When I changed out my Sonata's factory fill coolant with ST extended life concentrate and distilled water, it merely exhibited the customary "sweet" odor - a common characteristic of any ethylene glycol based antifreeze product. The only other thing I can think of to explain the possibility of contamination involves the bottling machinery. ST's antifreeze is almost assuredly sourced from Prestone (not exactly a newcomer to antifreeze technology, and certainly considered a reputable company). The back of the ST jugs does indicate that it's distributed by Alsip Packaging, Inc. I've posted previously that I believe Prestone ships the formulated antifreeze concentrate in bulk to Alsip Packaging who then bottles to individual gallon jugs, then cases and ships to WalMart's regional warehouses. I'm wondering if during a routine flushing and cleaning of the discharge machinery, either at Prestone's end or Alsip's, the holding tanks weren't completely emptied of the flush material. (If the stuff's shipped from Prestone by rail tankcar, who knows what was in the tankcar previously?...) If I'm anywhere close to correct, it's possible any residual "contaminant" is perfectly safe. Possible. On the other hand, if you're concerned at all about the long term effects on gaskets, o-rings, and waterpump seals, you may want to pre-emptively go through the flushing and refill again. Frankly, I couldn't blame you if you went with another brand antifreeze, but I don't believe either Prestone or ST per se are bad products. At worst, I suspect some minimum wage flunkie was asleep at the wheel.