Have you even looked to see where the oil might be leaking out?? I would think that you might want to do that first...y'know, look under the car, or in the engine bay...losing that much oil in a week would certainly make itself obvious.
Thanks but there is never a drop of oil under the car. The only indication is that there is smoke out the rear of the car when you presson the accelerator (maybe from exhaust but maybe not). Any other suggestions if it is coming from the exhaust?