Originally Posted by Quasimodem
I used a diesel additive (I think it was Amsoil, but I will edit this later when I have a chance to check my garage for which one I was using) for a few months in the proportion specified on the bottle.
I started noticing a slight "thump" when I started my car. Sounded sort of like a mild backfire.
I got lazy, and stopped using the additive. Starting thump/backfire went away.
I've used additives twice. Both times the engine had serious problems afterwards and I stopped immediately. The PS gray bottle didn't help a slight hesitation and I later found fuel line leaks which had nothing to do with the hesitation. The second time I used a fuel stabilizer and had the CEL come on, needing to replace NOx sensors and catalytic converters. Scared me away for sure, but the problems are likely not related to either additive. I find much more success just sticking with a particular brand and a busy station.
In popular culture, most vitamins are still touted for their original theoretical advantages by many, even long after the original benefits were disproven in scientific studies and in some cases, detrimental side effects were revealed. Vitamin E is a great example, as it has been touted to do different things over the decades and is known to cause cardiac arrhythmias. Vitamin C has had multiple studies showing no effect on colds, at least 23 of them. When one study showed a "possible" benefit, the true believers felt redeemed. Zinc for colds is basically worthless but its marketed on the basis of another very sketchy study that has had few if any repeat verifications. The thought process of evidence based medicine (EBM) exists because its the end points that count, not the mechanism or test that matters, having found examples of treatments that don't show any statistical advantage in results even though they somehow fix a parameter such as a test result.