Q: I accidentally poured a gallon of windshield washer fluid in the radiator overflow reservoir. What should I do?
A: If you have already run the engine, the two fluids have mixed. You should have the coolant flushed and refilled. Be sure to go to a shop that will actually “flush” the system, not just drain it. They should put a mixture of 50% antifreeze to 50% water back into the system. Also, check to make sure the shop uses an environmentally friendly way to recycle the old antifreeze. Depending on the coolant capacity of the system, the flush and refill process will cost around $75-$100.