The Belgium striker featured regularly under the Portuguese before his sacking in December and has since started just one of United’s eight Premier League games under the caretaker manager.
However, the 25-year-old conceded that the atmosphere has changed for the better under the new regime.
“It’s different, a lot more positive,” he told Canal+.
“People are smiling. At the moment everything is going well, and we have to continue like this. We’re enjoying it.”
Paul Pogba’s form has improved greatly under the Norwegian boss, but Lukaku believes everyone is reaching their top level again after a difficult start to the campaign.
“We tell him at training, Paul is happy, and then he laughs,” Lukaku said.
“At the moment, everyone is playing at their level. That’s what’s good. Paul, Marcus (Rashford), even myself when I play, I try to bring something to the team, Anthony (Martial). The competitive mindset is returning in every player.
“You see it at training when we do mini games, 6 vs 6, 8 vs 8, you can see the players are wanting to prove themselves to the manager because they want to take their chance, but the most important remains the team. That’s what's going to help us to return where we belong.”
