Identical narrative to my 2017 Countryman Cooper S All4 that ceased functioning last week.
Zero compression observed on cylinder two…
I was also operating BM3 stage 1, but with 91 octane. I also have significant reservations that the melody was the cause of its demise.
I discovered a service bulletin regarding the B48, indicating that the spark plugs must be oriented properly; otherwise, the electrode may disrupt the injector spray pattern and flame front, potentially leading to melted pistons and cylinder walls. Mercedes encountered the identical problem.
Interestingly, I replaced the spark plugs with Bosch ones approximately six months ago… I still need to verify whether the plugs have different threading, but Bosch claims they are not clock-specific.
I have been considering replacing the B48A20T1 from the LCI JCW models, but it appears to be a complex task due to the altered DME module and its utilization of a more recent "bordnetz" communication protocol compared to the 2017 BDC. Additionally, it necessitated replacing the transmission, although that would have been feasible.