I saw someone mention this stuff in another thread the other day and my first reaction as a confirmed cynic was 'what absolute b*llocks'
Marketing these days is so powerful all you need to do is put a picture of some guy off the telly on the advert (in this case Ed China) and you convince at least one person. That person then goes and tries to convince everyone who knows, if he succeeds then they all go off and it just spreads like wildfire, whether the product is good or not is largely irrelevant, no one actually considers this point these days, we just listen to the people that say what we want to hear and ignore everyone else.
Only thing I would put in my engine is oil. Any loose debris can be removed by changing the filter, maybe once in a while a good flush with oil.
Most manufacturers advise strongly against using such cleaning products too, they can and often do cause damage....