After completing a £22 million switch between the two clubs, the Netherlands international has settled into his new surroundings superbly this term to the tune of 22 goals across all competitions.
Even though the 29-year-old picked up the PFA Player of the Year award for his goalscoring exploits with Arsene Wenger's side last season, he feels he is still improving as a player at Old Trafford.
"Every day I work on new things. I become alert to small details that make me better. I go into work every day whistling," Van Persie told NOS.
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"I feel better and fitter. In the last week, I played Wednesday and Saturday. In those games I played with ease."
With the club having moved nine points clear of rivals Manchester City at the top of the league, Van Persie believes the attention to detail shown by the coaching staff, in particular fellow Dutchman Rene Meulensteen, has played a large part in that lead just as much as his goals have.
He added: "The way he [Meulensteen] trains is exceptional. He is truly one of the best coaches in the world.
"I have had a lot of good trainers, but it’s the way he prepares our team for games. Every match is different, so every training session in the build-up to games is unique.
"We know exactly what to expect and he wins points for us through his training. We’ve won a lot of games by the odd goal and they are point winners, which we train for.
"For instance, against Chelsea I scored after a low cross from Antonio Valencia on the right. It might seem a fluke, but the whole week before the game was spent working on that move.
"Training is really good. It’s a very pleasant environment to work in."