They r filled to a certain point from the dealer, I am sure the tanks are only rated for so much. My tank sure was fun to have but what a pain in the ass to change-out and refill
i have nitro.. bottles are only 11 for each trade in, but i just hate the hassle.. sometimes it lasts a little bit, sometimes it goes bye bye pretty quick.. depends how much you drive and how much you keep in your tank.