I would use an OBD reader (I use a wifi type and my iPhone with dash command ) you can monitor actual engine temps. You said temp didn't waver but the temp indicator on the dash is not really a gauge: it shows the same noon position from 75-115°C (or something similar, that is the buffer for the E46)

__________________
2011 E70 • N55 (me)
2012 E70 • N63 (wife)