To each their own. I like synthetics, all I've used since Mobil 1 was introduced over 30years ago. I also use additives, a .5micron MoS2 is my favorite in the oil (Mr. Moly), soluble molebdenum in limited-slip diffs, MoS2 in regular diffs and transmissions, RedLine Diesel Water Wetter in coolant, RedLine Diesel Catalyst in fuel, ... we have Chemists, Engineers, Scientists, ... they help to break down compounds and their uses / applications for me. Additives are already in oil (and other fluids), and are limited by the cost/benefit for the manufacturer. If additional additives bring diminishing returns in the market, they will not be added. You might not be buying the best oil in the first place, RedLine synthetic for example is made with a polyolester basestock that Mobil and Amsoil don't use, ... there's always a better solution if you don't mind spending the money.

Now the caveat.
Some additives are good, some are bad. The biggest problem for most people without chemists etc. is to determine which additives will help and which will hurt. Anything that will break down in your engine due to chemical or thermal reactions, shouldn't be there. For example: Many additives contain PTFE (or Teflon) which breaks down into a gummy mess at a temperature lower than the combustion temperature in your engine. That tells me that it can cause rings to foul and stick, as it breaks down and gets scraped into the rings/pistons. Bad. So, it isn't IMO whether additives can be good for the engine (they can), but which ones are good or bad for the engine. In theory, Boron (in the engine silk product) is good provided it doesn't break down or displace adequate amounts of another necessary compound in the oil. I'll stick with MoS2 for my additive of choice, but the Boron does sound interesting. Tetra-ethyl lead (sp?) was another very good lubricant, now banned by the EPA for use in engines, but you used to be able to add that to your oil.

__________________

Gone to the dark side

- Jeff