There are several versions of these out there at local gas stations and autmotive shops. A small bottle that you add to a full tank of gas.
They’re supposed to clean deposits from fuel injectors, but I have heard many other instances where professionals tell you not to add such additives as “oil treatments” because they can damage the engine and don’t work as they should (mostly infomercial type stuff)
So is a product like STP Fuel Injector Cleaner a good product to use, with no harmful side-effects?
We really don’t hear stories, or stern warnings from car makers, about fuel tank additives causing harm. By and large they’re pretty safe.
Many car makers sell fuel tank additives under their name. At least some of these are Techron additive, house-branded. Techron has a long history of safety and effectiveness. I wouldn’t hesitate to use it or a car-maker brand additve. I’d be a bit leary of some of the others, but I still doubt they’d cause harm with reasonable use.
In the field, I have seen some minor drivability problems solved with Techron. I don’t think it’s a bad idea to put a bottle in every 3 or 4 months for preventive maintenance. But as to whether a particular car needs it, or will benefit from it, it’s pretty hard to say.