What is the 2006 chevy silverado coolant type?

You should put Dex-Cool in Your 2006 Chevrolet Silverado. Specifically, it needs to meet the Organic Acid Technology (OAT) requirements, and also the performance requirements of ASTM D3306 and D4985. Or, more simply, You're going to want A50/50 mix of orange colored coolant. A good choice of this is AutoZone's NAOB53, which runs about $20 a gallon, and meets all the specifications from GM for Your vehicle. You'll need to switch this out every 50,000 miles, even though it's been known to last up to 100,000 miles. However, eventually the organic acids and silicates can separate and drop out of the solution, creating an abrasive reaction with the metal of the engine; given how cheap coolant is and how easy it is to change it, better not to risk that by waiting to long to flush and fill with new.