When you fill up you tires with air and send it out on the track they build pressure as they build heat. So if you send your car out on the track with 30psi it can come back in at 40psi. its a guessing game. Say you right front raises 10 psi, then you compensate by setting up your car 10psi lower when the tires are cold. when everything is up to heat and pressure starts to build hopefully you will be running where you want to be. Nitrogen eliminates that, it will only change 1 or 2 psi depending on track car weather ect.... and yes its really only effective at 100% nitrogen. why would you mix it anyway, just pick one!