If I have the rear brake drums turned would that get rid of the squealing brake noise. Any advice about this annoying problem would help.

I have a 5-spd 1993 Nissan Altima, 4-cyc, and I got around 350 miles to a tank when the empty light started to come on. Shouldn't this car get better gas mileage? The car is supposed to hol 16 gallons but whenever I fill up it only holds around 10 maybe 11 gallons, but the gas gauge is all the way on empty...is it just the fact that my gauge doesnt work and im not driving all of the gas out or what? WIth gas at like $2.50 a gallon I would like to increase my mileage as much as possible and getting 22 miles a gallon....I know 8 cyclinder cars that get better or atleast close, I should be getting like 25-28 or something shouldnt I? :wall: