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Andre Lotterer put in a strong stint in the #2 Audi to start closing the gap to the race-leading Toyota as the #1 car hit trouble.
Lotterer closed the gap to Stephane Sarrazin to around 1m30s during the final hour of his stint, showing consistent pace to chip away at the advantage enjoyed by the #7 Toyota. Just before 4am local time Benoit Treloyer took over the #2 car, but there were worried faces across the garage.
Lucas di Grassi took over the #1 Audi as it suffered a reliability issue which had seen Tom Kristensen slowly driving back to the pits going through power cycles to rectify the problem, with Audi revealing it had changed a fuel injector and got the car back out in a little over five minutes.
There was also trouble for the #14 Porsche as Marc Leib went in to limp home mode and struggled back to the pits, failing to emerge late in the session as Sebastien Buemi in the Toyata #8 closed in.
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Live text commentary recap of Hour 13: Key moments in bold
02:54 (UK Time)
In comes Sarrazin and he takes on a new nose before heading back out in the #7 Toyota in the lead
Lieb has made it back to the garage and Porsche goes to work while Lotterer hands over the #2 Audi to Treluyer
Cracking job from Senna who is now over 1m clear of the #74 Corvette as he continues to lead the GTE PRO class
Very painful for Lieb who is still only halfway through the final sector and running very slowly
Lieb radios in saying it's a fuel pressure problem which he is suffering from
Trouble at Porsche as the #14 limps back towards the pits. Lieb at the wheel and with five laps over Buemi in the #8 Toyota
Now the #1 Audi is in for a set of new boots and some fuel. Di Grassi heads back out after a short stop having been 3m04s behind Bernhard in the #20 Porsche in the final podium position
Bernhard immediately giving feedback to the Porsche hierarchy. Don't forget the 919 is still a new car that Porsche is learning about with every race
In to the pits comes the #20 Porsche from third place, with Brendon Hartley jumping in the car as Timo Bernhard climbs out
Lotterer continuing to catch Sarrazin for in the lead Toyota, the gap between the two now just 1m33s
The on-track battle for GTE PRO honours has gone a bit quiet, with Senna in the #97 Aston Martin 20s clear of Fisichella in the #51 Ferrari, although Fisichella just set a personal best and took over three seconds out of Senna
In comes the #8 Toyota with Buemi remaining in the car as he receives some more fuel and heads back out in a relatively lonely sixth place overall, six laps behind the #14 Porsche in fifth
Lotterer continuing to lap more quickly than Sarrazin in the race-leading #7 Toyota and the gap is now 1m36s
That's right, a full pit stop, driver change and fuel injector change and the #1 Audi car is running at full pace again after just over five minutes...
Di Grassi is straight on to the pace in the #1 Audi. In fact, he's the quickest car out there right now as he hunts down the #20 Porsche in third place
The gap at the front is coming down slowly, with Lotterer now within 1m40s of Sarrazin and 1.3s quicker on the last lap
Di Grassi brings the #1 Audi back out on track but it is down to fourth place and Lieb in the second Porsche is within two laps if any more trouble hits...
Apologies, the #20 Porsche passed the #1 Audi on track but was still a few laps down. Now Benhard comes past the pits to take over the last podium position while work continues in the Audi garage
The #2 Audi also pits and Treluyer takes over from Lotterer in the second-placed car. Sarrazin leads by 1m55s as we pass the halfway mark
The #1 Audi is wheeled in to the garage and di Grassi jumps in to replace Kristensen while the mechanics go to work
What did I say about the impressive recovery for the #1 Audi? Bernhard about to take third place from Kristensen... and that's it. The #20 Porsche up to third
Kristensen is in trouble in the #1 Audi! Going very slowly on the Mulsanne straight, he's going through 'power cycles' to try and fix the issue