Some1 told me its is bad for your engine, I would like if it is or not.

 

It depends on the booster. Gasoline itself has octane boosters in it, so not all are bad. Some are hard on different parts of the engine. Cheap ones tend to foul out your plugs with crud. Some put deposits on valves and so forth. The more expensive ones tend to have fewer side effects. I don't know of any on the market that are completely ok, but for most the side effects aren't a big deal. It just depends on what chemicals they used to boost the octane rating.

 

which 1's are good and which 1's are bad, I've used 1 cheap 1 I can't think of the name and NOS's octane booster, but I stopped because a mechanic told me not to use them, but sometimes even mechanics are wrong so I need some opinions and facts on this!!