This product works! No knocks or valve clattering at cold start. Oil consumption dropped from 1 quart every 1500 miles to nil. Fuel mileage jumped from 19.0 mpg to 21.8. Overall performance dramatically improved. So impressed,used product at next oil change in wife's 2004 Chevy Impala LS with 3.8 V6. Same results. Daughter drove the Chevy,swore it ran like a small block V8,had to pop the hood to show her the engine. Put the product in her 2002 Saturn,gets 35+mpg.