That is incorrect. Filling the diffs 100% you are getting an incorrect rating, almost double the blocking effect. You will also eventually warp your diff cases (If plastic) and blow the seals, causing leaks. This is really wrong information you are giving here Slayerphonics, I've been in RC 20 years, racing over 10, been to many different tracks and never heard ANYONE giving the advice you are. At least you are right to say that silicone is used because it's inert. The leaking is caused by the pressure changing direction rapidly as the diffs unload, that's why a full diff leaks.

Fill the diffs 55-60% people, like every instruction manual on the planet tells you.