Hiya forum guys!

I am a new pilot and i have a question about my flight time. I am in training at a local club. I Bought a nexstar select trainer to train on, as that is what most of the instructors at the club use to teach on, and what most of the trainees have to learn on. I must admit that i find this ironic because after buying this trainer they had me take all the training aids off the plane except the speed flaps! But alas i digress. Anyway, this plane has the OS .46 engine. I am not sure about the fuel tank size, but i believe that it is either 8 or 10 ounces. I fly at about 50% to 60% throttle for most of the time. We both use the 11x5 stock nexstar prop. I use 5% nitro fuel in the plane. I am getting about 11 to 12 minutes of flight time before the tank is empty. I was fine with this until my trainer brought his nexstar selectout that has the same engine and tank as mine. We fly his for over 20 minutes at a time. When i asked him about the difference, he said," Oh, your engine just needs time to break in." I accepted his statement and moved on.

At this point i have run about 8 to 10 tanks of fuel(the better part of a gallon) through the engine and I am still getting the same run times. The only difference is that the instructor uses 15% nitro fuel, and i use 5%. Our engines are tuned with the needle valve to the same pitch, so i am also assuming that the engine is tuned correctly. My enginedoes run a little richer. Should i consider stepping up to 10 or 15% nitro fuel to get these same run times? Or how many tanks of fuel will i run through this before my engine gets 20 min run times?

All in all i am having a blast with the hobby and my local club has been awesome.

Thanks for reading my massive run on sentences.