Gasoline is regulating in the USA to have below 95 ppm sulfur at the pump, which far lower than it has ever been, hence the minimal smell when behind a car in wide open throttle.
Gasoline in raw form is an emissions regulated commodity by region and then becomes unique through additives blended in at the tank farm or delivery point to reduce carbon build up and operating condition inprovements like cold winter starts, etc.
So, any brand of gasoline, today has very low sulfur content. Anti-carbon forming additives are really only the difference between brands: those above the EPA standard and those not.
So I guess that 95ppm being so low to begin with, there could not be that much in variance between brands, or even in different batches of the same exact brand, correct?
Also, none of them even claim to be lower than that 95ppm standard??