2007 Chevrolet Impala LS 07 3500 V6

You know we can't see what's leaking over a computer, but GM does seem to have a lot more trouble with corroded heater cores and radiators. Part of the problem could be due to the use of Dex-Cool antifreeze. GM advertized that as "lifetime" coolant to trick people into making the cost of maintenance appear lower than for their competitor's products, then on the reservoir it says "replace every three years". Even the Dex-Cool manufacturer doesn't recommend going that long before replacing it.

Antifreeze is always antifreeze, but it's the additives that wear out in about two years. THAT'S why we replace it that often. There's water pump lubricant in it but more importantly it has corrosion inhibitors that wear out. Acids form in the coolant from the combustion gases that normally seep into it. That's what leads to the corroded heater cores and radiators.

The issue with your car is not the low mileage; it's the years. The rubber hoses are not likely to be leaking yet, but if the leak is too slow to locate, dye can be added. After some coolant leaks out you search with a black light. The dark purple dye will show up as a bright yellow stain that you can follow back to the source of the leak.