My 2001 Toyota corolla is losing oil. There is no bottom-end leakage. I took off the head and there are no cracks and the valve seals are in spec. The oil started burning like crazy 5 years ago. I did some research and this was common for some cars according to what I read online. The dealer changes it and there is no problem. The car runs GREAT. My highway mileage is 34. changing oil once a year is fine. better than what most ppl do. frankly, if you do like 10,000 mi a year, that's about right. despite what ppl say.