The Polish striker believes Dortmund look different from the catastrophic form of last season and has backed his former club to push Bayern until the end of the season.
Bayern Munich forward Robert Lewandowski believes a title challenge from Borussia Dortmund can only be good for his side.
The Polish striker thinks the yellow-and-blacks look far better under new manager Thomas Tuchel and appreciates that their current form is keeping his own team on their toes.
Speaking to the official Bundesliga website, Lewandowski said: "Right now the gap is eight points, but we're not champions yet. It's best if we stay focussed right until the final game.
"We'll be fighting with BVB up until the final game. That's good for us, too. They're playing really well this season, in the Europa League as well.
"Last season was verging on the catastrophic and I don't really know why.They're a quality side with a lot of good players. They're playing a bit differently compared to last season.“
The Bavarian giants struggled to regain their form in the Champions League last season after effectively concluding the Bundesliga title in January.
With very little to play for in the league Pep Guardiola's side struggled to raise their game against better sides in Europe and were ultimately knocked out by Barcelona in May.
Yet thanks to Dortmund's title challenge, Lewandowski doesn't foresee that problem arising again this season.
He added: "We know what we did wrong last year, and I hope we do a better job of it this year.
"It doesn't matter if we have a five or eight-point lead in the Bundesliga because that's two, three games. Everything can change."
Bayern current sit top of the Bundesliga table, with Dortmund eight points behind them in second place. Guardiola's side travel to Hamburg next Friday to kick off the second half of the season.