So much depends on the engine, oil, driving habits, climate etc. My daughter just drove 1800 miles in 3 days to CO (all interstate) in her 4 cyl Mercury Mystique and she checked it there and states that it is still at the full mark. Engine has 92,000 miles and never really used any oil. It is running Amsoil Series 2000 0W30. Had about 4000 miles on the oil before she left. Will change it this Christmas when it will have about 10-12,000 miles on it. (90 degree heat here and it was snowing there today).
Now my Buick 3.8L SC will use oil at high speed, about 4 ounces per 1000 miles of high speed use and it has only 60,000 miles on it. Amsoil 10W30. No consumption around the city.