2001 grand prix gt. i average 17 -18mpg (mpg is not my concern). but I'm only getting about 220 miles before i have to fill up. I'm not waiting for the light to come or until its in the orange part. my dads 08 mustang gt gets like 320 miles before next fill up. something wrong? how many gallons left when in orange or when light comes on. my trip computer said i only had 42 miles left and that was before the light?