Why is the tear strength of the silicone mold weak?

addition-cureIn order to reduce the viscosity of silicone rubber and pursue a good quality, you may add a lot of silicone oil into the silicon rubber when making molds. In fact, it might have just the opposite effect. The tension and the tear strength will be reduced badly with the addition of silicon oil. And the silicon molds will be in a weak and flimsy manner.