Put one or the other in, but I wouldn't intentionally mix 'em just to save time. If your vehicle calls for DEX-COOL, and is out of warranty, G-05 would probably work just fine. (If your vehicle is still under warranty, though, while some would argue that G-05 is superior, it can also be argued that if you experience a coolong system failure, GM just might tell you to go pound sand if you turn in a warranty claim and you're not running DEX-COOL.) If you do decide to convert to G-05, just be sure to flush thoroughly (preferably with distilled water), and when you do install the new juice, dilute ONLY with distilled water. During the repeated flushes, when the water drains colorless and CLEAR, you've done enough. Figure on at least six flushes, idling until the engine comes up to temperature and the thermostat opens. (How hot the upper radiator hose feels is generally a good guide for this on most cars/trucks.) Don't forget to turn the heater's temperature valve all the way to, "Hot", since the heater core needs flushing, too.
[ March 30, 2005, 05:01 PM: Message edited by: Ray H ]