All gasoline comes from the same source(s). Gasoline is refined and processed and then piped around the nation. It is at the end of the line where it is pumped into company trucks (like shell, Chevron, BP, etc) that they add stuff to the gasoline. Those additives are in slightly different proportions depending on which company you go through, some companies add other products which may or may not actually do anything for your mileage or save your engine from excessive wear, deposits, blah. Your very best bet is to buy cheap gasoline from a mom and pop kind of station - while there get the gas tank additive and use as directed and on a regular but not always kind of basis. If you are worried about carbon deposits in your fuel burn, then drive your car/truck what ever longer and further. Carbon builds up when a vehicle goes for short (less than 20 miles) hops and is turned on and turned off. Like say running the daily errands. Each time the engine cools down and burns 'cold' more carbon is left behind - until the engine gets up to its optimal heat and maintains that heat to burn off the carbon. Other chemicals are also left behind and usually are burnt up in the catalytic converter (which is why modern cars have them) or in the process of a hot engine doing its thing for a period of time. Adding additives to the gasoline rarely makes that significant of a difference if your habits are contrary to a 'healthy' engine. As for things that wear out the engines - that's usually oil, oil filter and what not down that line. that is where the real dirt in the engine does the most damage. And as for the carburetor (fuel to air mixing contraption) the significant dirt comes from dirty air filters, not from gasoline. The real difference (and the reason why you pay what you do at the pump) is the name - like buying a name brand of anything - you pay more for that name than for quality.