At $12-14 per gal. of concentrate, I think it’s cheap insurance to drain, flush, and completely change with fresh antifreeze. Remember, it serves as a coolant also, and the heat breaks down the chemicals much more than the cold does. The rust/scale inhibition factor is another function of antifreeze, so as Jerry says, putting in fresh provides superior protection there as well. Antifreeze also acts as a lubricant for the water pump. I think you’ve gotten your money’s worth after 7 years!! Time for some fresh chemicals.
