I saw that same deal. My temp on my n55 seems to read low and I'm wondering if the sensor is just sending slightly incorrect signal. I had thought my tstat was reading wrong but my coolant pump failed and I replaced the tstat with it (n55/e70) and the temps still read lower than target and lower than oil temp by a fair amount. Wife has n55 in her 535 so I'll have to take a test drive and compare

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