The problem isnt cynnicism, Im sure the chemists can come up with something that does as it claims...
The difficulties arise when folk with little knowledge ( Moi !? - a little knowledge is a dangerous thing!) try to make the decision as to when/if it is a worthwhile compromise...For to be sure, I'll wager there are downsides. Ive seen enough medicine to know drugs are not great at working in conjunction with other medicines. This can tie doctors in knots, and worse still for patients sadly....!
As a wet clutch biker, 'additives" has long since been a dirty word...! Not understanding the chemistry, or even the environment into which is to be placed ( ICE, oils, the various materials used in modern manufacturing, or even not that modern perhaps) all play a part in throwing the wrong gunk down the gullet of your favourite V8....
So I s'pose, there's no arguing with it if you prefer to roll up your sleeves and rip a car down down if it belches smoke occasionally ! It doesnt mean there isnt a product that couldnt do useful work on a specific element of the motors function. The problem lies in trusting the market place to pitch a product that has been carefully derived and robustly tested. Enough for the same market place to be clear about their products limitations...
but as Dave's assertion makes clear...there's oil in those there cylinders, and it aint sposed to be there...the Q is, why/how did it get there....? And why only sometimes does it push past whatever keeps it at bay...?
Bucket chemistry, voodoo science and anecdotal evidence...my three favourite things !