We picked up our new '08 Prius on Saturday, my jaw almost fell to the floor when the finance guy told me about the maintenance plan and the fact that the car requires an oil change every 6 month or 8KMi, whichever comes first ? Shocking, financially and environmentally speaking. I got the pitch about Prius oil not being synthetic and degrading with time, so ... why doesn't Toyota use synthetic oil instead ? The engine revs to 5000rpm max, it should easily stand 15 to 20Kmi and up to 2 years with the same oil, just like contemporary Audi and BMW do, with variable intervals to maximize oil life. Even high revving engines (Porsche, Ferrari) do with yearly oil changes. Does anyone have a technical explanation for this aberration ?