The 2018 TE 250i and 2019 250i/300i have a very specific spark plug designed specifically for optimum combustion and fuel mixture generated by the injected models. For this reason, spark plugs from earlier models must not be used as otherwise it can lead to poor starting and engine running behavior.
NGK Spark Plugs serves as a lighter to ignite the air/fuel mixture under extreme conditions. A spark plug must dissipate the heat produced by the combustion gasses.
Spark Plug Compatibility checker: http://www.ngksparkplugs.co.za/ngk-catalogue/