I have a 97 camry and was losing a quart of oil a week. I found out it was due to Engine oil sludge condition. I checked it out on the Toyota website and found that there is a Customer Support program, a.k.a. it is Toyota's fault and they will pay for it. I had to have my engine rebuilt and the valve cover replaced, which did fix the problem, at no cost to me. It's worth checking in to.