When to change your coolant
Take a look at your car's owner's manual, or the recommended service schedule in every Haynes manual for suggested coolant change intervals. Some models need a change every few of years but some modern cooling systems are considered "lifetime fill" from the factory. Remember, when a manufacturer says something will last a lifetime, they mean it will last longer than the warranty, typically 5 years or 100k miles.
If you don't know the last time the coolant was changed, and the car is more than 4 years old, change it now. Part of the cooling system service involves flushing (draining, filling with water and draining again), but if you change it regularly flushing isn't needed.
You should always check the radiator and heater hoses when draining the system to change the cooland and replace any that are old, cracked, or swollen.
All cars are slightly different, so if it is time to change your coolant, use our before you begin checklist, and find your car for specific instructions.