adding oil at Le Mans in the past and present?

[djb]

This question came up with a friend recently.

I thought that in the past at Le Mans there was a "no adding oil" regulation, or only so much per certain number of hours or something like that. Am I completely off-base with this? It seems to me that there were even wired shut oil caps to ensure this, with folks inspecting them to make sure there wasn't tampering.

Am I mixing this up with something else, and if not, when did this change, as nowadays don't they add oil if need be? I could certainly see the point of restricting adding oil to a leaking engine just to make it through to the end, whilst slowly leaving a trail around for the others to fall off on.

thanks,
David