Rubber compounds containing high level of precipitated silica are notoriously difficult to mix and process. A short test procedure (< 5 minutes) enables the assessment of both the reaction between silica and added silane and the critical influence of temperature on silane degradation. The results obtained with a RPA2000 testing machine clearly demonstrate a "MIXING OPERATING WINDOW" for temperatures of 140 to 160 C. An improved mixing procedure was developed which would ensure optimum silica compound properties for both silica "silanisation" and low silane degradation, By using highly dispersible precipitated silica's and an improved mixing procedure for minimum silane degradation, it was shown that degree of silanisation correlates with the mixing energy. Above of that, by using the RPA2000 the advantage of TESPD over conventional TESPT when mixing at high temperature was shown.