So, all these wonderful "engine cleaning" additives the petrol companies supposedly have in their petrol. Are they an actual thing or are they just fancy names for "benzene"?

Funnily enough, they don't seem to want to elaborate on anything beyond the fact that the additive is there. I've no doubt that the chemical composition is a closely guarded commercially sensitive top-secret thing, but has anyone done some investigation?

Sounds like BS, the last time I saw a clean running engine cracked open before the advent of these additives, it already looked pretty clean to me.