In the early 1970s, BMW began adding the small-case letter i to certain versions of its models. The letter spread throughout the range, and in case you’re wondering, it stands for “injection”, referring to the fuel supply of gasoline engines.
Recently, BMW announced a new variant of its X3, this time called the X3 M50. Many took notice that this time, the “I” was missing, and questions started being asked. According to BMW Blog, which questioned the company on it, the answer is that it will henceforth be reserved for electric models. At BMW, BEVs’ designations start with the same letter. This was confirmed to the site by Bernd Körber, BMW's Vice-President of Brand and Product Management.
We can expect to see the i disappear from the names of current gas-engine models. The only other situation where the letter "i" is used is with the iDrive multimedia system, and that’s not expected to change. This isn't the first time BMW has played with its naming structure, and we’re now far removed from the days when the numbers in vehicle names were linked to engine size. Today, with the proliferation of turbocharged 4-cylinders, the link between the number and the size of the powertrain is no longer as strong as it once was.