The Gunners can take advantage of the lunchtime kick-off to move eight points clear, and would be nine ahead of Manchester City, if they can overcome Manuel Pellegrini's men, who are on the back of a morale-boosting Champions League victory away to Bayern Munich.
Wenger expects a much-improved display from their last visit to Manchester, when a slow start resulted in a 1-0 loss at United in November.
"People forget that United had two shots on target on the day and they scored a goal off a shoulder (of Robin van Persie) from a corner, but on the day, I believe we were not completely ourselves offensively and that is what we want to do better tomorrow, to be dangerous offensively," Wenger said.
"However, a team is not set there (following a poor performance). After they do it, they grow.
"Sometimes if they do it they stop, learn from it and then grow again.
"It is what we want to show at City. We learn from it and we go again."
Wenger wants his team to play with freedom and expression, rather than be hampered by the pressure of leading the title challenge.
"I don't see why you should be scared," he added.
"Last season when we went to Newcastle on the last day and we had absolutely to win you could think 'if we don't win it will be a disaster', but today we are in a position where we can look much more at the game in a positive way."
Wenger, though, warned Arsenal will have to be on their guard against City's expensively assembled squad, which has been irresistible at home this season, thrashing United 4-1 in September, while sticking seven past Norwich and hitting Tottenham for six last month.
"We need to make sure we have the ball," Wenger said.
"When they have the ball they are dangerous: (David) Silva, (Yaya) Toure, (Sergio) Aguero, (Alvaro) Negredo - they have potential to be dangerous.
"For us, it is important we have the ball."
Arsenal smashed their transfer record on deadline day with the £43million signing of Mesut Ozil from Real Madrid, but that spending was already way behind that of new City boss Pellegrini, who invested almost double on five players after taking over in the summer including Brazilian midfielder Fernandinho from Shakhtar Donetsk and striker Alvaro Negredo from Sevilla - all bankrolled by Abu Dhabi-based billionaire Sheikh Mansour.
While Wenger accepts City's "unlimited financial resources" will for now put them at an advantage, that does not always necessarily translate into a sustained title challenge.
"In England you have so many teams who can win the league, nobody can guarantee they will do it before the season starts," he said.
"We have Manchester United, Liverpool, Arsenal, Chelsea, Manchester City, Tottenham who wants to win it, Everton now look to be a contender (also), so it is impossible to say 'mathematically we will win it'."
Full-back Bacary Sagna could return from a hamstring injury to play against City.
The 30-year-old is out of contract in the summer, but Wenger revealed a new deal was expected to be agreed shortly. He said: "That could be decided in next two weeks."
England forward Theo Walcott is pressing for a first start since his recovery from minor abdominal surgery.
The 24-year-old has announced he and wife Mel are expecting their first child, which is due early next summer.
The couple said in a statement: "We are both very excited at such happy news just a few months after getting married. We are really looking forward to becoming parents."