No additives please
Alot of the premium gasolines have some sort of top tier additive in them and the additives are at a prescribed rate.
FYI they are called top tier because they are designed to work on the upper engine, ie valves and combustion chamber.
However, many believe that they simply move deposits down in the ring pack.
One more thing to be vary much aware of, and this LSPI, low speed preignition.
Direct injected, turbocharged engines are highly susceptible to this phenomen.
It is extremely important that you use the specific Motorcraft oil for this application. The pre ignition is a function of some of the additive systems in modern engine oils. A new category, ILSAC GF-6 is coming out shortly that addresses LSPI and any oil licensed as GF-6 will be fine in your application.
Dexos Gen 2 licensed oils may work as well as there are engine testing protocols to cover this.
Bottom Line: Be careful adding anything to oils, coolants, etc. Sfest thing I can tell you is DON't!
2013 BBK Short tube, E-Force Stage 2, M/T 275/15/60 DR's, BMR LCA's with lowering brackets, Alum D/S, Strange FRT adjustable struts, strange adj rear, whiteline pan hard