I rember talking to a guy that runs a repair shop, this happened in the late 90's , he was selling Amsoil Engine Flush, I wanted to buy it, he warned me that they were having some problems, people were putting it in as to the instructions, and a week or so later they were having leaks and major engine problems, the gentleman told me that the Amsoil Engine Flush and those so called engine flushing machines were breaking of big chunks of debris that was getting clogged inside the engine, he said that he wished they made a product that worked more slowly, now we have Auto-Rx. Think of a giant icicle hanging off a skyscraper, with Auto-Rx it drips harmlussly down on the pavement, with those engine flushes and engine oil flushing machines that giant icicle comes crashing down on the pavement causing damage to anyone it hits, I like the drip of water hitting me so I will stick with Auto-Rx. Let's not forget that it takes many miles and sometimes years for sludge and carbon to form in our engines, I doubt a 20 or 30 minute flush is going to correct everything, I will let Auto-Rx do the job versus tearing my engine apart to clean everything.