I think you did the right thing. If you did not put the coolant in yourself, and did not know what was added. But, using the universal coolant is fine. I've been using it since it came out, and has never given me any problems. The coolant I use is a lighter green than conventional coolant, and will mix with Dexcool without any issues for topping off. Then when I change coolant at recommended times, just drain and flush old, and add the new universal. I've done this with all my GM vehicles, and never had an issue. I even compared the ingredients on the Dexcool with that of the universal coolant I use, and it is the same, other than the color. Doesn't really matter the brand or color, just as long as it has the same ingredients. Now in the Honda Civic I own, I only using Honda blue coolant. As previously stated, they use HOAT, and I've seen folks really mess up by using other coolants in those vehicles.