The sale of additives for fuels and oils moves millions of euros each year and many of us have considered this at some time.
Personally, I am not in favour of their use and in general I am very suspicious of miracle products... the more miracles they perform, the more suspicious they make me.
What we have to be clear about is that additives do not repair, at most they mask a problem and, above all, they are expensive and can cause incompatibility problems.