Auto-Rx does not fill in scratches on the cylinder bore. However it will clean out carbonous materials in the ring packs that may have caused some scuffing of the bores. Other than re-honing the cylinders, there is no product that actually fills in scratches effectively. Those that make those claims forget to tell you that their products do, but for a very short time.
Most poor ring sealing is not due to scratches on the walls of the cylinder bore. In the majority of cases low compression is due to coked up deposits that bind the piston rings together, so that they can not flex and effectively seal against the cylinder wall. Auto-Rx will clean out any contamination out of the sctrches so that oil has a better chance of filling in the scratches from the oil film that is constantly renewed as the motor runs.
