Where do you add the antifreeze coolant Cadillac STS?

To add antifreeze coolant to a Cadillac STS, locate the coolant reservoir, which is typically a translucent plastic tank near the front of the engine bay. Ensure the engine is cool, then remove the cap and pour the appropriate coolant mixture until it reaches the recommended level marked on the reservoir. Always use the type of antifreeze specified in the owner's manual to maintain optimal performance and prevent engine damage.