I have a Toyota Corolla 2001. It has 99000 miles. It runs fine. Today I noticed that the oil level was almost at half mark within a month of oil change. It was on full mark when the oil was changed at 98000 miles on Dec 1, 2008. In the past at one time there was no engine oil in the car, in fact the engine oil was changed just about 3 months back. My mechanic did tight something, may be a valve, at that time. I never show oil on my garage floor. If the engine oil is reducing where is it going and how to fix it? Thanks
Some cars use oil. Your probability of not using oil goes down substantially when you found no engine oil in the car. Some oil can be consumed in the normal process of operating the engine.
On the other hand, if you are saying that you are down a half quart in 1000 miles, then most of us and nearly all manufacturers believe that is within normal limits. Check your oil level more frequently, refill when needed and change your oil once a year or every 5K miles or so. I would not obsess over this.
I have not much to add. You should get in the habit of checking oil often. Also check it when you get home anytime someone changes the oil. If you change the oil check it the morning after you have driven it.