I know that this did not work for me on my 2000 Toyota Corolla. I did not get it until about 55,000 miles and it had been used as a rental. The first time I had the oil changed they let it drain for about 15 minutes or maybe longer and told me it took forever to come out. I knew then I had sludge problems. I followed the instructions at the time and even went through a second full set of the sludge instructions and through both of these my oil light would come on and even some times you could hear the engine like it was not getting oil. I got more out of using semi-synthetic oil or synthetic oil then I did using auto-rx. I know it works for some but for this car it did not work. I even used it in my transmission and had to dispose of this car after 92,000 miles because when the car got hot it would not engage in reverse as it seemed to go into neutral. I decided it was not worth it and bought another car.