It is best to use one of the case-bond glues between the cases (These sealers smell like airplane glue when curing).  Case-bond is oil resistant and semi drying.  RTV/Silicone that smells like vinegar when it cures is not really oil resistant.  Over time silicone swells up and looses it's adheasan.

Ultra grey and ultra blue is not a RTV type silicone it is more closely related to threebond 1211.