My Toyota Prius is using about a quart of oil every six hundred miles. This started when the car had approximately 90-95 thousand miles. Before that it didn't use any oil. It has been checked by two different mechanics and there is no leak. After researching on the Internet, I found out there are many Prius that have the same problem. Toyota is definitely aware of the problem, yet takes not responsibility for it. My Toyota dealer mechanic said, "it is no big deal, just keep adding oil." I believe Toyota knows exactly the problem is causing so many Prius's to have the same problem but doesn't want to admit anything.