It's an oil temp gauge, the better to avoid exploring the engine's rev range
until it reaches operating temperatures (the tach also has lights which move
the redline upward as the oil warms up). You can retrofit the cluster, but
I don't think it'll be easy to make the oil temp or variable redline
The E39 cluster must be programmed to the car's ECU and evidently those
advanced functions aren't easily enabled. But the gray gauges and trim
rings sure look nice!
R / John
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