Manual tank selection can make A HUGE difference depending on the plane. in the Spits, there are a top and bottom tank, (and wing tanks in the 8). I burn the wings first, as they are easily damaged. then burn the top, to lower my center of gravity. sometimes i'll leave 1/4 in the top as a reserve cause I have a tendency to ignore the gauge while engaged. In planes that have wing tanks, and torque issues (like corsairs) you want to burn the wings first, and Leave 1/4 to 1/8 in the wing opposite the engine torque to help counter it. then switch to main.