my friend has a retired po car and we used to fill the windshield washer fluid res. with diesel and run the spray lines into the intake manifold and we would drive into parking stuctures and such (no plates of coarse) and we would hit the deal to spray the windows, and we would have diesel injection! the car would be revving really high and going nowhere, and it smoked really really bad (to the point of no visibility)...then we would just drive out of it and take off....for a week after that the car would run like ****, but then it was all good...your bit o diesel will just make you smoke a bit...I wouldn't go through thte hassel of draining the tank (especially for .5 gal.)...your friend is a retard...