I think they are adding some sort of a flushing additive and circulate it to your car's cooling system. Is that additive not harmful to the radiator? I remember once my brother-in-law had his mazda 323 radiator flushed in a gasoline station. After few days, his radiator started leaking. Because of that, I' thinking of just draining my radiator of old coolant and fill up with fresh water, circulate for few minutes and drain it again.Then add a fresh mixture of water and coolant. Will that be okay guys?