In my 2018 Highlander with the 3.5 Litre V6 D4-S GDI/PFI engine, the manual says to add a bottle of fuel system cleaner to the gas tank at the 10,000 mile (16,000km) service. This is the Oil Change interval as well BTW.
Upon asking the dealer they said this is to aid in keeping the engine deposit free as depending on driving pattern the PFI combination with the GDI might not do enough to keep it entirely deposit free. Also to guard against lower qualities of gasoline when Top-Tier isn't available and non top-tier is used occasionally/frequently.
I just want to know what's in it, if it's just a healthy dose of PEA and nothing more is all.