I've been using the Sonus Der Wunder MF drying towels and really like them, but I've noticed that the more I wash them the less effective/absorbent they are becoming. I've followed the manufacturer's washing directions and washed them in warm water, used no fabric softener and dried them in the drier, but the last time I tried to dry my car with one it just seemed to push most of the water around. Anyone else experience this? What am I doing wrong?