My car is quite old, has roughly 165k miles and has had about 5 to 6 unknown previous owners, so I decided to try out Rislone to hopefully quiet my loud engine idle and to hopefully remove some sludge. Immediately within a few seconds or so with a full bottle Rislone in the crankcase, I noticed the loud engine idle smoothen out and became quiet, so quiet that if I was to stand behind my car. I wouldn't know if the car was on or not. I'll most definitely be buying Rislone for my car in the future.I recommend a full bottle of Rislone in your crankcase if you're looking to perhaps improve the performance of an old car like mine, or your new car. Rislone reduces friction and wear, so that your engine can run smoothly while increasing it's lifespan, and to perhaps slightly improve your MPG. Use Rislone for general maintenance every oil change or so, quiet your loud engine idle, slowly remove sludge and to make you and your car happy. I am satisfied with Rislone and I hope that if you try Rislone that you'll have excellent results.