can just barely split
Tony, realy big? We used to cut into the end of the log with a chainsaw, pour in about 3/4 cup black powder, insert fuse, cover with clay or play dough light it and run for cover. It splits logs in half or throws them in the air or both but it does split them. For four foot in diameter and up. Your local police may pay you a visit if loud noise upsets your neighbors.
The log spliters, to get around the oil tank problem, always in the way, Square steel tube welded to the under side of the "I" beam works well for an oil tank and stiffens the beam so it can handle the really big pieces without bending the beam.