The Pole dominated the Spanish mixed-surface event, leading from the first stage to take victory by 5min 15.8sec from Saudi Arabian Yazeed Al Rajhi.
It was the fifth WRC 2 win of the year for Kubica, who drives a Citroen DS3 RRC, and gives him an unassailable lead in the championship ahead of November’s final round in Wales.
“This wasn’t the target at the start of the season but somehow I knew that if I was able to learn quickly on gravel I could do a good result,” he said.
“I was pretty sure that on tarmac I was quite competitive but the rallies in the World Rally Championship are completely different to each other. In the end we managed five wins and one second place from the six rallies that count for the championship - so all good.”
Apart from a broken handbrake that affected his pace in tight corners, Kubica had a trouble-free rally. His rivals however fared much worse.
Elfyn Evans was Kubica’s closest challenger until he took a wheel off his Ford Fiesta R5 on Saturday’s street stage in Salou. The Welshman rejoined on Sunday but stopped again with a broken clutch after the opening stage.
Skoda Fabia S2000 driver Sepp Wiegand held the runner-up spot throughout Sunday’s competition until he stopped after Stage 12 with broken transmission.
Al Rajhi, the WRC 2 winner in Sweden, had a solid rally in his Ford Fiesta RRC. It was another good result for the driver who withdrew from the championship over the summer while he recovered from a serious back injury. “I really enjoyed this rally, everything for me is going well and I learned a lot. I’ll be back,” he said.
Robert Barrable finished third in WRC 2 and 15th overall in his Tunnock’s World Rally Team Ford Fiesta R5. The 26-year old dropped out of winning contention on Saturday when a broken driveshaft relegated him to 45th place.
“To finish third, against such strong opposition, is okay, although I’m a bit disappointed with our pace on the second day,” he said. “To have completed all the stages and reached the finish on my first visit to Rally Spain has given me invaluable experience.”
Subhan Aksa was fourth in another Fiesta R5 with Nicolas Fuchs fifth in a Group N Mitsubishi Lancer EVO X.
Enrique Garcia Ojeda led the category from the very first kilometre in a Citroen DS3 R3. The Spaniard eventually won by 16min 55.3sec and finished a remarkable 13th overall.
United Arab Emirates driver Mohamed Al Mutawaa was second, with fellow countryman Mohamed Al Sahlawi third, a further 13min 27.7sec behind. Both were also in DS3 R3 cars.
There were no other starters and Sebastien Chardonnet clinched the title in France last month.