Prius manual recommends 0/20 oil which is very much suitable for Winter. But now winter is going so for better results & year round use, 5/30 would be the best choice with 5K interval.
But choose good quality oils from Companies like LM, Kixx, PTT.
If want to choose for longer intervals upto 8~10K, then choose 5/40 from same above companies. But change both filters in the mid way like after 4~5K.