If it is indeed the sump / block joint which is leaking, there are three products which will ensure leak-free joints until the engine goes to the big place in the sky....
1) Hylomar - originally a Rolls Royce product taken over by Loctite - it remains pliable and works better than anything else I know of, even on casings with known small imperfections - that's why it is used by many motorcycle repair shops to seal crankcase casings.
2) Grey RTV as sold by Delta. It can however only seal very accurate surface joints.
3) High-heat Copper silicone - cannot remember the manufacturer but available from most spares outlets. Sets to a tough but pliable joint sealer.
I suggest you prime both surfaces to be sealed together with Loctite Primer - else a thorough wipe with thinners will also do.
2011 VW Amarok BiTdi 4-Motion
2006 Daihatsu Sirion
6 x Water Buffalo's