Dillmann, 25, has replaced Tom Blomqvist on the Indonesian-backed Jagonya Ayam scheme run by Gelael's father Ricardo.
The deal represents a big break for Dillmann, who previously raced with Carlin in GP3 and F3 but has struggled for budget in GP2.
"I want to thank Jagonya Ayam for this amazing opportunity," he said. "I look forward to showing what we are capable of once the season gets under way."
The 18-year-old Gelael (pictured right), who tested FR3.5 machinery last autumn, said: "I'm happy to be staying with Carlin - having had the opportunity to test the car I'm very excited about the season ahead."
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