Mix the sour cream, mayonnaise, vinegar and oil. Then season with salt, pepper and dill to taste.
You could also replace the sour cream with sour cream, yoghurt or something similar. The dressing is enough for a small bowl of salad for 1 - 2 people as a side dish.
Goes very well with cucumber salad, we like it best with peeled cucumbers, but also with mixed salads with cucumbers.