I have to agree with the others on this. I would suspect that a lot of the oil is being consumed via valve guides. If you are leaking that much you will have tremendous puddles every where you go, not to mention that all the oil that is undercoating your car, at least it won't rust :-)
Also it has been my personal experience that Mobil 1 gets burned very rapidly by older 103 engines. I would recommend getting rid of the Mobil 1 and get some real oil. I switched to Redline. You should also be careful not to assume that because there is no blue smoke that no oil is being burned. Six cylinders with worn guides can burn a lot of oil and not foul the plugs.
The best way to watch the leak is clean the area thoroughly and use an inspection mirror to see where the oil comes from.
92 Volvo 740 Wagon aka "Mutt mover"