Hi just my experience ,had noise/ rattle on tick over , went when clutch dipped ,told by dealer technician when checked normal ,I think it is likely a noisy clutch thrust release bearing .Really noticeable if you are parked next to a wall /house as in my drive where the noise is amplified .This is in the bell housing so gear box oil/ slick 50 probably make no difference .This & the poor first to second gear change when cold I believe are not uncommon .I was not very impressed also being a 296, 07 car I was concerned with poss/ oil consumption issues talked about .Car now sold , rattle never got any worse , so as others have said nothing to worry about just annoying . regards chris