Statistics can be of invaluable help when measuring success and failure in sports. There are instances though when statistics don't end up giving the complete picture, but more often than not it gives a clear idea of a trend. If one looks at the stats of IPL winners, it is quite clear that Mumbai Indians have been the most successful franchise in the history of the league so far, with 5 titles.
CSK are the only team to average below three, with Mumbai Indians coming in at the second spot. Mumbai have been outstanding in the league since winning their maiden title in 2013, but it is their performances in the initial seasons of the league that puts them in the second spot.
Both Mumbai Indians and Chennai Super Kings would want to improve their record further but they will have more competition now as two new teams, Lucknow Super Giants and Gujarat Titans, have also entered the fray.