The lead changed hands on six occasions on rock-strewn dirt roads near the Spanish border before the Belgian Thierry Neuville took a 17.7sec advantage in his Hyundai i20 over Elfyn Evans. Dani Sordo was a further 6.6sec adrift in third.
WRC leader Sébastien Ogier, previous round winner Ott Tänak, Toyota Yaris team-mate Jari-Matti Latvala and Hyundai duo Andreas Mikkelsen and Hayden Paddon were all sidelined as the gruelling roads took a heavy toll.
Neuville’s gamble to select soft tyres for this afternoon’s second loop of three speed tests appeared to have backfired as temperatures rose and the tracks became rougher than expected.
He held his nerve and jumped from sixth to first as bedlam broke out around him, retaining his advantage over two asphalt stages in the streets of central Porto.
“Today was tough but we managed to stay out of trouble. It was very rough and there were many, many surprises so I tried to save the car a bit. It was a risky tyre choice which was maybe not great but we made it work,” he said.
Evans held second in a Ford Fiesta until a spin dropped him down the order but the Welshman vaulted from seventh to second in the twists and turns of the final dirt road stage.
Sordo topped the leaderboard midway through the leg in his i20. Like team-mate Neuville, the Spaniard opted for soft tyres this afternoon but regretted his decision and had to slow as they became worn.
Teemu Suninen was fourth in another Fiesta, the Finn avoiding the carnage to trail Sordo by 10.1sec and head Esapekka Lappi in the sole-surviving Toyota Yaris by 11.4sec. Mid-leg set-up changes resolved Lappi’s traction problems.
Mads Østberg was sixth in a Citroën C3, half a minute clear of team-mate Kris Meeke, who twice led. Tyre troubles forced Meeke to drive the final Porto stages with just a wheel rim on the rear left of his car and he conceded a minute.
Ogier was fourth until he broke a steering arm in his Ford Fiesta after hitting a tree root and he crashed at the next bend.
Tänak hit a rock and damaged his engine’s cooling system, forcing him to retire from the rally. Toyota’s turmoil continued when Latvala hit a rock and broke his front right suspension.
Paddon retired from the lead after a heavy impact damaged the front left of his i20 and blocked the stage. The Kiwi was taken to hospital for precautionary checks after complaining of back pain. Broken power steering accounted for team-mate Mikkelsen.
Tomorrow’s (Saturday) leg is the longest of the event, journeying east of the rally base in Matosinhos to demanding roads in the Cabreira Mountains. Three stages are driven morning and afternoon covering 154.64km.