That depends upon your flying.

At full throttle many better ported .46 engines will consume about .8-.9 oz per minute.

But we really should not be flying the planes flat out all the time.

With an 18oz tank I can fly for a good 20 minutes+ until the tank runs dry.... however I set my timer for 14 minutes, to give me a few minutes of "going around" time if the pattern is busy or someone is out in the field retrieving a plane.

We had one guy flying a Telemaster with a weed wacker gas engine one day. His throttle got stuck at 60%.

After thirty minutes of non-stop flying, he gave me the controls because he was tired, and I flew his plane for another 40 minutes before handing it back to him.

The plane flew for 1 hour and 28 minutes before it ran out of gas....