Having been kept on his toes by Jari-Matti Latvala in the morning, Loeb immediately doubled his lead with a commanding win on Hohlandsburg-Firstplan.
Latvala still managed to go fastest on two of the afternoon's four stages, but the Ford driver's margins of victory were smaller, and he completed leg one in France 13.1 seconds down on his Citroen foe.
Mikko Hirvonen, the only man who still stands a remote chance of denying team-mate Loeb the 2012 title, is now just over half a minute off the lead in third.
Hirvonen is only 0.7s ahead of Petter Solberg's Ford as the Norwegian picked up his pace in the afternoon and started chasing a podium.
Citroen Junior's Thierry Neuville had been Hirvonen's biggest threat in the morning, but a spin on the afternoon's first stage dropped him to seventh.
Neuville spent the rest of the day trying to take sixth back from Dani Sordo's Mini, closing to within a second only to lose time with another spin on Mulhouse. He still stayed ahead of seventh-placed Mads Ostberg.
- Mikko Hirvonen