Both anecdotal non scientific experiences. First, daughters car I placed a bottle of Neutra in the oil about 500 miles prior to annual oil change at Christmas. (Amsoil 0W30) This is a 4 cyl Ford Zetec. Had the car 5 years now has 75,000 miles. Anyway, over the past four months driving back and forth to college she has been checking her mileage, amazing according to her, gettting 34-35 mpg on the highway whereas previously in low thirties. Perception or reality, don't know but I never asked her about it she volunteered this info. Placing the Neutra in the gas had no effect but she adds an oz of Amsoil PI at every tankful anyway.
Second case, friend of hers has a Honda that at Spring break she was complaining only ran well if an OTC fuel injection cleaner was placed in every tankful and it weas getting expensive and a hassle. Otherwise engine stalled, idled rough etc. I gave her a bottle of Neutra. Saw her last night and asked about the car. Her comment, ever since I placed the stuff in that yellow bottle into the tank the car has run fine. No more fuel injection cleaner needed every tankful.
Again, not science just personal stories.
Second case, friend of hers has a Honda that at Spring break she was complaining only ran well if an OTC fuel injection cleaner was placed in every tankful and it weas getting expensive and a hassle. Otherwise engine stalled, idled rough etc. I gave her a bottle of Neutra. Saw her last night and asked about the car. Her comment, ever since I placed the stuff in that yellow bottle into the tank the car has run fine. No more fuel injection cleaner needed every tankful.
Again, not science just personal stories.