Jari-Matti Latvala exploited favourable road conditions to dominate Friday's first full leg at Rally Guanajuato Mexico and build a half-minute lead over team-mate Sébastien Ogier.
Starting the high-altitude gravel speed tests eighth in the order, Latvala benefited from roads swept clean of dirt by those ahead to win all four loose surface special stages and head Ogier by 32.1sec.
The Frenchman endured the worst of the conditions by running first through the dusty mountain roads and was powerless to restrain Latvala. He regained a few tenths of a second on the three short spectator tests in León, but faces a tough task to preserve his unbeaten start to the WRC season.
"I'm happy with the gap tonight," said Latvala, who will again benefit from the road conditions in Saturday's leg in his Volkswagen Polo R. "I have to be a bit careful and patient because I don't need to take all the time in just one stage."
Ogier drove on the limit and was far from disheartened. "I'm happy so far. This afternoon was very good. I've been pushing as much as I can and couldn't do better," he said.
Dani Sordo held third all day in a Hyundai i20 to end 1min 15.6sec off the lead. The Spaniard was unhappy with his car's handling and a sticking throttle ensured nervous moments as he fought to keep the i20 on the road.
Norway's Andreas Mikkelsen topped the times in León's street stage, but an overshoot and handling problems upset his chances of closing on Sordo and they were split by 31.1sec.
Hayden Paddon and Mads Østberg fought for fifth all day and were separated by 14.8sec at the close. Both regretted their choice of Michelin's hard compound tyres this morning, Østberg labelling the decision as 'one of the biggest tyre mistakes I've done'.
He was penalised 10sec for a jump start while Paddon damaged his i20's suspension after swiping a wall and burned his hand while making repairs. He also slid into a ditch after his car mysteriously filled with dust in the final mountain stage.
Ott Tänak was seventh in a Ford Fiesta RS despite a spin and what the Estonian believed to be a broken differential, while Martin Prokop, Lorenzo Bertelli and WRC 2 leader Teemu Suninen completed the leaderboard.
Thierry Neuville retired in the opening stage when he spun into a bank and broke his car's suspension, while Eric Camilli dropped many minutes with a puncture and later lost first and second gears.
Saturday's second leg is the longest of the rally. Drivers face six gravel tests in the mountains north and east of León before two short stages at the city's motor racing circuit and a night test next to the service park. It adds up to 152.40km of action.