Originally Posted by elpappy

Additives in gas are long-term things, there is no way a different additive package is going to make a car run better from tank to tank. The additives have nothing to do with friction. Perhaps after 20K miles, the engine will be slightly cleaner with a different additive package, but it's not going to run better the first time you switch to a gasoline with a different additive package, anymore than thinking the car is running better because you change the brand of motor oil you use.

All cars seem to run better after a wash. Sorry, but people's perception about how well their car is running is extremely subjective and is subject to all kinds of interfering "noise" (weather, humidity, ambient pressure, traffic, etc.) that make subjective judgements extremely unreliable. All the objective data says that gasoline from the same area and time of year is the same from all the brands, except for very minor differences in the additive packages which can't possibly affect the day-to-day running of the car. Those are the facts.