this is exactly why i reset my trip odometer when i fill up. idk if its a mazda thing or what. when i had my first b3000, i would get about 100 mi each for the first 2 quaters of a tank then only a little over a hundred more for the second half of a tank. my second b3000 i would hit 150 miles per half a tank evenly. the tanks were comparable sizes (only a few tenths of a gallon difference, about 19 gallons plus or minus). in my 3 i am generally getting 200 miles in 3/4 of a tank, then generally hit over 300 by the time the low fuel light comes on.
on that note, after i fill up, my trip computer will say i have 350-370 miles remaining, but will always zero out shortly after the light comes on
07 Mazda3 s Sport HB, Phantom Blue Mica
Moonroof, Auto-Dim Mirror w/ Compass, Stripped Side Molding and rebadged, Front Air Dam
OEM 6 disc/MP3 changer, 300w x2 amp, 2 JBL GT4-10's
K&N Typhoon Series CA/SRI