Lets revive this thread. The Hybrid market is very ripe, and although Toyotas are much more resilient to local deformities such as "lower quality petrol" and "less than ideal engine oil grades" compared to other brands, the hybrid principles apply to the entire range of brands, whether it's the Honda Fit Hybrid, the Honda Vezel, or the Toyota Prius.
Let me start with sharing my Prius (now at "genuine" 90,000 km) experience in 1.5 years of ownership:
1. Only used 5w-30 oil ONCE due to lack of availability of 0w-20.
2. Last two oil changes were Liqui Moly 0w-20. It only recently became available.
3. Absolutely zero "oil" consumption. Engine in perfect condition. So that myth is busted.
4. Fuel Economy (what it all boils down to). My aim has been from day 1 to return 19 km/l within the city. I only use V-power and in the city with A.C, the current cycle reads 14 km/l at half tank (My on board meter has been very accurate somehow!) Previous cycles on V-power have fluctuated between 16 km/l and 17.5 km/l. I attribute this largely to the unreliable quality of fuel. It feels like even V-power isn't particularly reliable.
5. Fuel Economy (still searing): I learned that if you go through even slightly longer trips (shahrae faisal for instance) that involve constant speeds, the car does as much as 30km/l on that run without sweat. Only about 10% of my commute involves Shahrae Faisal or similar, hence, the fuel avg per tank is quite less than my original aim of 19 km/l. Bummer.
To sum up, 0w-20 can safely be used IF:
1. You don't have a VERY high mileage prius.
2. You're 100% sure the meter hasn't been reversed. =)
3. You HAVEN'T been using a different grade of oil the past SEVERAL changes.
Lets keep learning and sharing people!