I would assume you dont have anything more than a 10oz tank approx 1 oz a min of burn time. You could however have an 8 oz and be getting good fuel consumption rates. Thats pretty normal IMO. I have both ends of the spectrum a 40 size profile 3D plane with an 8 oz tank and a YS .63 on it I get about 7 to 8 mins of flight time. Then I have a Giles 300 60 size with a 16 oz tank and a Saito 100 in it. I get about 15 to 18 minutes of flight time. SAitos suck fuel like demons. I had an OS 91 on it and I was almost getting 25 minutes of flight time out of it. I dont think theres a problem at all it sounds normal to me but to make sure yo uneed to find out what size tank you have in there.