Washing powder

I'm not loyal to any particular brand, but I try not to buy a biological product. I use liquid detergent for darks and powder for whites. I quite often buy Persil powder because it's what my mum used, but I'm using Daz at the moment, a bargain at Lidl a while back. My husband tells me to stick with this as it's doing a wonderful job on his hankies, pristine apparently and only Daz has managed this. I wash most things on at 40 degrees, would only contemplate 30 for delicates, apparently, in spite of previous advice, a 30 degree wash will not kill bacteria