oil consumption

When you excessive oil consumption how many miles does it take for the oil to go low 1 quart? less than 1000, less than 500, less still? 1 quart every 1000 is still really good, according to the engineers who designed the motor. 1 quart every 500 is the beginning of a problem. Any blue/gray smoke? Only on start up, then you have valve seals and or guides going. All the time, then possibly rings. Any oil on the ground? If so, then you have a leak(s) that need to be fixed.