Based on research it has been found that the refining parameter that has a significant influence on the density of the alloy, as a controllable factor and also responsible for porosity, is the content of the introduced mixture of NH2. For this reason, the article shows the effect of the content of the refining mixture (90%N+10%H2) on porosity (qualitative and quantitative) and selected mechanical properties (Rm; R0.2, A) of AlSi7Mg alloy, used for die-cast automotive rims. It was found that the use of this mixture during the refining of AlSi7Mg alloy in a ladle with a capacity of about 2.000 kg provides the best results in terms of reducing porosity and improving mechanical properties when its content does not exceed 19.25 l·min-1. (approximately 55 s. of introduction into the alloy). Exceeding these values causes both deterioration of porosity (qualitatively and quantitatively) and hardness, as well as selected mechanical properties. The research was conducted at Superior Industries Production Poland Stalowa Wola under industrial production conditions.