The wear metals in the oil will cause elevated injector and fuel pump wear. Keep in mind fuel pressures can reach 4,000+psi and the components pressurizing this fuel are very precise and require clean fuel. I would recommend installing a two micron final filter in-line with the original final filter if you plan on keeping the car.

With that said, I will agree that a $500 car is the best to experiment with, and you will probably save $500 in fuel costs prior to any measurable wear occuring inside the fuel pump or injectors. I wouldnt do this to a car unless I considered it junk at that point and had another reliable way to get to work. But the money saved is considerable. I know when I worked for the marine industry some of the large Sulzer, Wartsila, Niigata, and DDC/MTU diesels would actually have a setup that would allow them to run off their own crankcase oil, and they would measure how much was removed and constantly replace it until the oil had basically been flushed completely. Of course these engines burned bunker oil that was the consistency of grease at room temp, but its the same basic theory, although I can assure you they took filtration extremely seriously, for the oil in the crankcase, the oil being burned, and the fuel being burned.

Good luck, keep us updated on how it works.

__________________
Matt
2003 Jetta Wagon TDI 145,000MI
1999.5 Jetta TDI 287,000MI
2001 Suzuki SV650S 26,000MI
2008 Yamaha Vino 125 11,000MI
http://www.crazymatt.org