Using beer gas (N2/CO2 mix) won't help at all. Equilibrium carbonation level is determined by temperature and CO2 partial pressure. If you reduce the CO2 partial pressure, the carb will go down over time. If you are killing a keg in a day or two, this probably won't matter. But, if you want to serve a keg over a few weeks, you have to maintain the CO2 partial pressure at the equilibrium value for the carb level. If you switch to beer gas, you have to increase the total pressure in order to keep the CO2 partial pressure constant. For example, if you are using 10 psig of pure CO2, that constitutes a CO2 partial pressure of 24.7 psi (absolute pressure = gauge pressure + atmospheric pressure [14.7 psi @ sea level].) If you were to use 60/40 N2/CO2 beer gas instead of pure CO2, the total pressure would have to be 24.7 psia + 24.7 psia * 60/40 = 61.7 psia, or 47 psig. You would get the same amount of O2 in the keg from the "contaminated" CO2 either way. In addition, you would also get additional O2 depending on the O2 contamination level of the N2 supply.
The reason commercial establishments use beer gas to serve lagers is to compensate for long lines, and elevation increases from the storage area, Longer lines and elevation increases force a higher serving pressure in order to maintain the desired pour rates. If you used pure CO2 at the higher serving pressures, the carb level would increase over time.
Brew on
