0W and 5W doesnt matter here in Pakistan.. They represent the cold start temperatures. 5w is good for temperatures below 0'c.. So it is of no significance that we use 0w or 5w oils..
Meanwhile the viscosity rating of 20 and 30 is debatable.. Hybrids like prius don't constantly use the engine.. So a thinner oil is recommended.. 20 viscosity grade is hard to find. so 30 might be your choice..
We own a Prius and a Passo. Both recommend 0w20 oils.. I didn't have much info abt oils in the past so i put toyota's 5w30 in the prius.. and it has somewhat affected the drive in a that i dont feel it to be smooth enough and the engine on and off is more louder (but am talking about a little difference) .. but the mileage and all is perfect..
Meanwhile i put 5w30 liqui moly in my Passo and the car is running very smoothly with a slight increase in mileage.
Will like others to share experience regarding use of oil with 20 viscosity.. as m planning to change the prius oil to 0w20 in the next interval..