My '88 Escort (518,500 miles) has been using more oil than usual lately. I know it has some sludge problems and think maybe the rings are coked. Anyone have any suggestions of what might be used to clean this up without engine dis assembly. The car can still be driven like this and the car isn't worth the time and effort to dis assemble everything. Would it hurt to pour an ounce or two of Marvel Mystery Oil directly into the cylinders and let it soak for a few hours? Would this likely help break it loose and clean it up or more likely to cause worse problems?