Washing up liquid seriously? It will freeze after a cold snap, and streak. I did it once as I thought it would be better than just water, I was wrong.
Yip seriously. Screen wash also freezes and costs more. As I say I don't use mine much in the frozen winter unless its really dirty. No I don't get streaks as the wipers see to that. Its worked fine since I started driving in 86 and it will work fine in the future. As for leaving streaks over the rest of the car, so what. Its winter and dirty anyway. Ill wash it come march.