But Spa is only 1000km. If memory serves, Le Mans is nearly four or more times longer, depending on how many laps the leader completes. Now the math might be wrong, but if Peugeot consistently run at a pace seven seconds faster than the old lap record, and Audi are only running at that old record pace, Peugeot are going to catch them once every thirty laps (assuing everything remains constant). Audi would be doing 15 laps an hour (not allowing for pitstops), so they'd be caught once every two hours by the Peugeot. Thus, over the course of the 24 hours, they would be caught 12 times. The winning Audi did 369 laps last year, and assuming that they didn't have pitstops (which it obviously did, but I can't work out how to factor that in, nor do I want to because it's late), that means that if Peugeot win under the above circumstances, they'll have completed 381.
Now, I do actually have a point here: La Sarthe is 13km around (I'm rounding down). 369 laps of a 13km circuit means the 2007 winners completed 4797km. If the Peugeot wins with 381 laps, they'll have done 4953km, which is 156km further. Now that might not sound like much, but it's 12 laps and 156km more in which something could go wrong. And it's at the end of the race, usually when the engines have been running for nearly 24 hours, so there's more chance of there being a problem. Might not be much of a chance depending upon how the car is built and handled by its drivers and teams, but there's still an increased chance.