not sure but if you're using top tier fuel companies, you're already getting fuel additives. that is the only difference between the gas at the pump. it all comes from one pipeline point for all stations in the area and they add the "shell additive" when they fill the tanker for delivery.
I don’t know about fuel additives that needs to be added x amount of miles but at every oil change I add a can of seafoam to the gas tank if anything it’s keeps the tops of the Pistons and combustion chamber and injectors clean the motor is a Direct inject motor so it is not doing nothing for the valves I do the oil changes every 7000 miles
No but Hyundai/Kia does and I've always through it's a good idea just to run a bottle through every 5-10k miles. Techron is good stuff but I use the Liqui Moly Direct Injection stuff instead since I already plan on using LM for oil once I get my 2nd free oil change.
I filled up with 91 octane ethanol free last time for grins since the manual claims that max hp/torque specs are for 91.
I noticed an immediate difference - it was more expensive ($5.69/gal)!
Runs the same.