The pair were teammates at Stamford Bridge during Lukaku's first stint in the Premier League with the Blues.
"I still speak to Didier. He gives me tips all the time," Lukaku said.
"We have had a really special relationship since day one.
"When I arrived at Chelsea they put me next to him in the dressing room so that is when it started and I saw what a top professional he was
"Didier was a leader. When the team needed him the most he always delivered so that is what I aim for and hopefully one day I can say I was that type of player.
"I text him, I phone him whenever I need him. He knows what to say and what not to say. That's what I like about him."