Sks jamming problem???????

i got an sks awhile back and we took it shooting..it shot fine..jammed every now in then,then we took it apart to clean figure that would help..it was nasty dirty but we cleaned it up really good, and now it jams after every shot, it wont kick back to ejec the shell..like aat all, my brther was thinking we used the wrong oil, that maybe it needs a heavyer grease, idk if anyone has any suggestions thatd be nice :)