I look into fuel additives when a car is getting up in miles. I found a great store online that has information about the different fuel and engine additives you can get for different vehicles. I found out the first one was made by Bell in 1909! The additives for gasoline and diesel engines began early in the car and engine making industry. I remember that PTFE was popular for a long time for pouring into the oil. PTFE is just another name for the brand of non-stick coating they put on pots and pans.
Another interesting thing I found out about additives for engines is that bleach is used in some of them. Bleach, or sodium hypochlorite, is extremely slippery. If you have ever gotten any on your fingers you would know. I have no idea how it reacts in the long term with engine oil and the different metal and plastic parts it would come in contact with. Yes, there are plastic internal engine parts. Way back in the 1970s a timing gear on an old sedan my mom owned was made out of nylon.
We use fuel and oil additives as well as transmission additives to squeeze out a little more performance or longevity in motor vehicles. Reducing friction is a big help to engine life. I would say the some additives really do increase compression when rings and valves are wearing out. I had a transmission shop that has been in business for decades recommend a transmission fluid additive for my old midsize sedan.
The website I found that is a great store online for vehicle additives has a lot of information available about the different ones on the market. I learned what to use for an oil additive, a fuel additive and a transmission additive.