The pair, both driving similar Renault Clio Rally4 machines, shared spells at the top of the timesheets during a frantic opening day on Sao Miguel Island.
Mabellini was fastest out of the blocks. He ended the morning loop almost 30sec clear of his rival, but Fotia responded by pulling back a whopping 31.9sec over SS4 and SS5 to snatch the lead.
A minor gearbox issue for Fotia in the closing stages enabled Mabellini to move back ahead and the Italian finished the day with a tiny 3.7sec advantage.
“It feels good,” Mabellini told FIAERC.com. “We are happy with our pace and the car was perfect all day.
“Let's see what tomorrow can bring us. We are also hoping for better weather,” added the Italian.
The remainder of the leaderboard consisted of Clio Trophy by Toksport WRT runners, with Paulo Soria leading the Rally5 charge. The Argentine suffered broken rear suspension on the penultimate test and ended 2min 49.8sec behind the leading pair.