<<Exxon, amaco, and others have been fined for saying there gas cleans, or gives more power etc...>>
Actually, they were ordered by the govt. to stop saying that their premium grades would help your car. Bottom line is, unless your car spark knocks, higher octane doesn't help at all. In fact, it may hurt in the long run. (carbon build-up)
<<Over time all those little peices of dirt settle to the bottom and if the gas gets low its more easy for them to be sucked up. >>
All fuel pumps have their pickups in the BOTTOM of the tank. That's where the dirt is. Fuel level is irrelevant as far as the pump picking up dirt. All pumps have screens on the pickup, so any dirt passed is VERY small, and will be caught by the filter.
<<But the main reason is when you get to 1/4 or lowwer you can slosh the gas around and suck air. The gas is what Cools the fuel pump as it runs. When it sucks air, its like your engine running without oil. Mind you it will not destroy it doing it once or twice, but it puts a lot of stress on it and will shorten its life. And in tank fuel pumps cost a lot.>>
More or less true. You shouldn't run the car under 1/4 tank anyway, unless you know your gauge is wrong. Your pump would have to suck a LOT of air in its lifetime for it to do much harm, though. Depends on your car type whether running under 1/4 tank is uncovering the pickup or not. Most cars still have several gallons left when on dead empty. And yes, in-tank pumps are expensive.