I'd agree with lemonade...unless you have a BMW, then I'd recommend using BMW's own screen wash.
I've lost count of how many times my washer jets got blocked on my E91 using any other screen wash than BMW OEM stuff. I now only use BMW's concentrate in the M135i and haven't had any problems so far. I bought a 20 litre container of concentrate for ~£50 from the dealer and it will make up to 200 litres of diluted, depending of course upon how diluted you make it.