I felt compelled to give my testimony about the tremendous results I have witnessed with Auto-Rx. First off, I let my engine get tremendously, extraordinarily sludged up due to neglect. By the time, I realized it the engine, (according to Nissan) was beyond repair. Though I was still driving, I had a heavy white smoke at every startup, and from time to time, some sensors were going out, affecting acceleration. I heard about Auto-Rx by googling engine repair and ordered it, because I did not want to give up on my engine. I tried the Fast Track, but my engine was just too dirty. Within 200 miles, my car was jerking and lurching, still smoking so much, I had to get an oil change. My car could only go one week without the acceleration problems before I had to get another oil change, but I was determined to keep my car. Finally, getting tired of the smoke, I put my car in the shop, and they manually cleaned the engine the best they could in an effort to get rid of the smoke problem. But after I got it out, I STILL had smoke, not a great big cloud at every ignition, but every other day. I went back to Auto Rx for help. This time, my engine could drive the full 1500 miles with the product in the engine (I couldn't find anyone to change the filter only). But I used a new bottle at the 1500 mark. During this time, the smoke eventually killed my catalytic converter (still under warranty thankfully) and I had to have my transmission replaced (not sure if that had anything to do with the oil/smoke). But in the end, Auto-Rx made the smoke DISAPPEAR, something the mechanics could not do. My engine purrs again and Auto Rx saved me thousands of dollars! I will swear by this product and plan to continue to use it for another cleaning phase (still idles too low) and then maintenance. Thanks so much for this amazing product!