At 10 minutes into the hour, Fernando Alonso pitted in the #8 Toyota for the car’s scheduled stop. Due to the hybrid cars needing less fuel and being able to go an extra lap per stint, they had now pitted one less than their non-hybrid competitors.
Kamui Kobayashi then pitted the #7 Toyota a lap later, with the gap to Nathanael Berthon in the third-placed #1 Rebellion standing at two minutes 20 seconds.
Halfway into the hour, Stoffel Vandoorne in the #11 SMP was rapidly catching Berthon, with the gap down to 17 seconds when Vandoorne completed his fuel stint and pitted. Berthon also pitted two laps later, meaning the gap after the stops between the two equaled out to 19 seconds.
Putting the non-hybrid pace into perspective, while the 2016 and 2017 pace from Audi, Porsche and Toyota was quicker than the Rebellions and SMPs this year, before 2015, the pace of this year’s non-hybrids and the pre-2015 hybrids is around the same, according to Paul Truswell on Radio Le Mans.
Meanwhile, Andre Lotterer in the #1 Rebellion had caught back up to the main LMP1 pack to sixth place behind Egor Orudzhev in the #17 SMP, although Lotterer was still a few laps back, with four laps’ gap to the leading #7 Toyota.
Near the end of the hour, the Toyotas both pitted, with the two cars receiving new noses in addition to the usual fuel. Meanwhile, Vandoorne had halved the gap to Berthon as the hour ticked over, with Orudzhev a further 24 seconds back.
The fourth hour of the race has been dominated by a superb battle at the front of the LMP2 order between the (now leading) #26 G-Drive Oreca of Job van Uitert, and the #36 Signatech Alpine of Pierre Thiriet.
As the fourth hour began, Signatech reclaimed the lead courtesy of the 10-second pitstop penalty previously placed on the #26 G-Drive entry for a Full Course Yellow infringement. During this stop, Nicolas Lapierre finally handed over the #36 Alpine to Thiriet, who would hold a 13-second lead over van Uitert at the end of the first flying lap.
However, Thiriet would soon start losing time, losing over four seconds over the next flying laps of the cars’ respective stints.
Elsewhere, Stephane Richelmi had been extracted from the #38 Jackie Chan DC Oreca and expressed concerns with the pace of his car – which had been running third – relative to the top two. The Monegasque driver said that the car was tricky to drive, and admitted to making several small mistakes that increased the time loss.
The reeling in didn’t continue at quite such a rate, but with 22 minutes of the hour in the books, the gap between the top two was down to within four seconds. By the half-hour mark, the lead battle was fully engaged, with van Uitert all over the back of Thiriet.
The pair were slightly split by traffic and a recovering Rebellion LMP1, and both pitted with 40 minutes of the hour in the books. Appropriately, both of the Oreca-built chassis left pitlane nose-to-tail, immediately re-engaging in battle.
Elsewhere in the order, there were dramas in the last quarter of the fourth hour for the #49 ARC Bratislava Ligier. Henning Enqvist struggled to recover the car after a spin at gentle barrier tap on the exit of Indianapolis, and needed to pit for a nose change. The team didn’t lose any positions by virtue of already being at the back of the LMP2 order.
With eight minutes of the hour left, van Uitert finally dispatched Thiriet on the run down the first portion of the Mulsanne straight. As the hour concluded, the pair were still within two seconds of one another.
Away from the lead battle, third place is held by Gabriel Aubry (#38 Jackie Chan DC Oreca). The young Frenchman runs almost a minute behind the lead battle, and is 22 seconds clear of Pastor Maldonado, who runs fourth in the #31 DragonSpeed Oreca.
The Corvette #63 entry continued to control the race, not feeling any effects from its earlier stop under full-course yellow. The crew took their fifth stop near the end of the hour with the bulk of the field. Mike Rockenfeller would be at the wheel in the lead at the end of the hour.
The only exception was the #51 AF Corse Ferrari, which is slightly off kilter after having to come in twice in the last stint because of the full-course yellow.
As the race has hit its stride, the gaps are bigger, but for much of the hour there was a three-way battle with the #93 Porsche of Patrick Pilet, #67 Ford of Jonathan Bomarito and #68 Ford of Joey Hand; they continued to battle hard throughout the hour.
However, after a pit-stop infraction (unsafe release), the #67 car was taken out of the action. The penalty was served at 25 minutes through the hour, dropping them to ninth in class.
Others suffered drama, as Richard Lietz in the #91 Porsche was involved in a fight with the #92 Porsche of Laurens Vanthoor and the #64 Corvette of Tommy Milner. Lietz locked a tyre going into Arnage, resulting in losing two positions in the battle and giving himself a big vibration for the remainder of the stint.
Lietz would fall to seventh at the half-hour mark, losing about two seconds a lap to those around him.
Elsewhere, there was a great fight between the #68 Ford with Joey Hand and the #92 Porsche of Laurens Vanthoor. The Porsche was on a charge at the end of the hour, pulling off a great pass in the Dunlop Curves and reeling in the top three at a rate of two seconds a lap.
Vanthoor immediately pulled the gap on the Ford and was battling the third placed #51 AF Corse Ferrari at the top of the hour.
The pitstop cycle would not change the order of things in the race with the exception of the #82 BMW, which would have its pitstop put under investigation.
Additionally, the #64 Corvette of Marcel Fassler and the #71 AF Corse of Miguel Molina were issued 10-second penalties for full-course yellow infractions.
Differing strategies started to emerge in the class, as shown by the #77 Dempsey Proton Porsche, which led at the start of the hour. Unlike other cars in the class, it pitted 20 minutes into the hour, taking its fourth stop earlier than the rest. This dropped Julian Andlauer down to third in class by the half-hour mark.
However as the pitstops rounded for the rest of the field, the car would again find itself at the front. This leaves an interesting tactical battle at the had of the field. When the #77 Porsche is in the pits, the #85 Keating Motorsports Ford holds a handy lead over the #84 JMW Ferrari. The #77 Porsche has enough pace to sit in third even when out of sync with the rest of the field.
For the rest of the field, after being involved in a fight earlier in the race, the #62 WeatherTech Ferrari had an extra stop, its fifth of the race, to drop it slightly out of touch for the lead in fourth.
After its earlier drama, the #90 TF Sport Aston Martin had resumed normal service in fifth.