The Citroen driver won four of the day's seven stages to finish 29.7 seconds ahead of Finn Jari-Matti Latvala in a Ford.
Finland's Mikko Hirvonen, Loeb's team mate and his only rival for the championship, was 54 seconds off the pace in third spot.
"It is good to have widened our lead," Loeb said having started the day 13 seconds clear. "I tried to enjoy the dry conditions and I was comfortable.
"We do not know what to expect for tomorrow, it may rain, the roads will be trickier, so I'm glad to have quite an edge."
Norway's Petter Solberg, who was fourth overnight, had to retire after his car ploughed into a vineyard and took down a telegraph pole, damaging the front of his Ford.
Qatar's Nasser Al-Attiyah also went off the road and injured two spectators.
Loeb is 61 points ahead of Hirvonen at the top of the overall standings.
- Mikko Hirvonen