I was told by several good people that you have to resleeve a block and replace the psitons with oversize pistons once you pull the pistons because the block bores wear in an oval fashion. It makes no sense just to pop new piston rings on there. Is this true? I am rebuilding a Diesel with Mercedes shop forum help right now.

On my 240D I didnt resleeve and I used Deves rings ant a year later it blew oil like crazy. On my Volvo diesel rebuild I lost no oil.