There is no fuel additive that will increase mileage. This is a myth. None of the snake oil additives work.
By adding a fuel additive in the gas tank you are going to get better gas mileage. It cleans all the injectors and all the fuel lines and the rest of the system.
Probably the best way to get better fuel mileage would be to get a tuner for it.
Fuel additives are used to improve an automobile's environmental performance and increase its mileage. Some homemade fuel additives are ethanol and a mixture of acetone, xylene and cycle oil.
The best way to get better mpg's is with a tuner/programmer. Most out there guarantee better fuel mileage.
Two independent studies rated Opti-Lube XPD as the best diesel fuel additive.
The H3 gets the best fuel mileage. Everything but the body is a Chevy Trailblazer.
The gasoline that is recommended by the manufacturer is the best fuel to use.
My opinion is that Cerma Stm 3 is the best fuel additive. I use it on my pickup and I went from 17 to 20 mpg's. After you add it to the fuel you'll need to change your fuel filter because it does a really good job cleaning the gunk out. The website explains it in better detail than I can. To learn more about it check out related links.
They are about the same in fuel mileage but the 6.0 is thirsty.
get a better car
Better mileage
diesel.