What should the oil temperature read on a peugeot 406 hdi 2003?

To the best of my knowledge the 406 does not have an oil temperature gauge, what it does have is an oil level gauge. This system samples the oil level when the ignition is first turned on and displays it for 30 seconds or so when the engine is started. When active the lights behind the needle also come on. At the end of this period the lights go out and the needle drops to the "off" position.

It does not monitor the oil level continuously as the oil level in the sump falls when the engine is running due to the amount of oil pumped into the upper reaches of the engine.

Hope this helps.