Two problems related to engine burning oil have been reported for the 2009 Toyota Prius. The most recently reported issues are listed below.
My 2009 Toyota Prius has 100,700 miles on it. When I took it in for it's last oil change I was informed that only a little over a quart of oil drained from the engine. I have religiously changed the oil every 3,000 miles. After replacing the engine oil it still looked dirty. The engine is burning oil. I understand that this is a common issue caused by a piston design flaw and does not have a cheap solution other than adding oil at each gas fill up. I am concerned that the engine may stop working while driving, particularly if traveling on a long trip at highway speeds. I do not feel safe driving this vehicle on a long trip.
Once my car got past 100,000 miles, the non-specific warning light started coming on and the word "problem!" would come on the screen. Manual says to ask dealer what the specific problem is. Certified Toyota dealer kept saying they don't know. Turns out after my own persistence that the problem is heavy oil consumption. Not burning; not leaking. Just high consumption. Take car for regular maintenance and it seems Toyota is aware of the issue, but keeps pressing me to get a new engine, rather than offering any intermediate solutions. Could have told me thousands of miles ago to at least keep adding oil, but they never bothered. I now know after about a year that I have to start adding a lot of oil just a few weeks after the oil is changed and filled. If I wait until regular maintenance interval, all oil will be gone. Engine would have broken down if I didn't persist in figuring out what was going on. Went through 3 regular service appointments before I realized what was happening on my own. Problem was at its worst when braking, but light came on at other times as well. I have yesterday's date here on the complaint, but this has been happening about a year.