2025 BMW M3 — coolant slowly disappears without an obvious leak — trying to narrow this down

If it were in my driveway, two 2025 BMW M3s can feel identical and have different causes, so measure before you copy someone else's repair. Save the big job until that test fails. That's the sequence I'd use. Not trying to scare you — just skip the expensive first guess. If that fails I'll eat the diagnostic fee.

Ask what changed right before it started. Swap the cheap/easy piece first on the 2025 BMW M3 and see if the fault moves. That's the branch I'd chase this week. Time, temperature, and whether it's in gear are the notes that actually help a shop. A day of patience here is cheaper than a wrong part. Might be overthinking it, but I'd rather overthink than overspend.

I wouldn't throw parts yet. Move a coil or plug on the 2025 BMW M3 if it's cylinder-specific and see whether the code follows. Save the big job until that test fails. This is from a 2025 BMW M3 in Charlotte. No need to make it theatrical. Wrote this up on my lunch break.