Fuel additive

I've never added any injector cleaner.
The manual recommends to use Hyundai fuel injector cleaner, of course...lol.
The manual also states, "if top tier detergent gasoline is not available" ,add the cleaner. I think it's standard for fuels in Canada and USA contain detergent additives so it cleans as you drive.
I think the only time I'd add any is if I noticed the engine stumbling, running rough or if I noticed fuel economy taking a hit.

yeah I've never used any for about 20 years and I only used them on carburetor cars, never on injected cars like we have now, and I always use the proper gas but I was just wondering because of the Hyundai motors using two types of injectors and have read different things about how these injectors work and can affect the engines.

Here is a write-up I did on our Venue's multi port, dual injector system. It's different than direct injection systems where a high pressure fuel pump is needed and the injectors are subjected to cylinder pressure.

I use a can of seafoam cleaner when it says in the service manual . It keeps it running nice.