It will depend alot on your flying style. If you set your throttle to max and leave it there, it will burn fuel more rapidly. Most .40 sized engines I have experienced (mine and other's) will run for about 10 minutes on an 8 oz tank, full throttle 85% of the flight. My ASP .40 sips so little fuel that I get 15 minutes of flying time (1/2 throttle 80% of flight, full for 15%) and I still have plenty of fuel at landing.