Sorry I took a bit of time to reply, as I was on holiday abroad.
The person who said "changing 0W20 and filter for 4 weeks...same as overhauling..." Well news for you clown, 0W20 was the STANDARD oil recommendation for the 1NZ-FXE from the factory. So wrong answer.
Putting 0W20 or 5W20 or 5W30 or even 20W50 WILL NOT fix ANY of the oil consumption problems! As I stated before, there is a complete TSB from the Toyota (The company that manufactured your Prius and knows better than ANYONE else). They fitted low tension piston rings on the affected models up till 2010. You can only repair this by installing the NEW, UPDATED part from Toyota that is a higher tension piston ring set. That is it. No additives, no oil will fix or repair your problem.
You will HAVE to open up your engine and you will HAVE to replace every piston ring inside.
I have done these overhauls before, but I do not have time and I would charge a lot to get this repair done, because I have to dedicate at least 1 to 2 full days, APART from my working business. All I can recommend is find someone who has a set of micrometres, bore gauges, torque wrenches, honing tool (NOT BORE CUTTING TOOL!) and PLASTIGAUGE. If a mechanic have never used or does NOT know what these items are, STAY AWAY from that mechanic.
