Coolant temp vs Oil temp

[ohyes]

Hi guys I just recently noticed that my coolant temp is lower than oil temperature? Does this mean anything or is worth taken in consideration?

Im on C5 X7 2.7HDI

Thanks for any thoughts!

[Stickyfinger]

When did the box last have an oil change ?

[Paul-R]

I think that ohyes is talking about the engine oil and coolant temperatures.

[Stickyfinger]

yes, he would be...........getting my coat

[xantia_v6]

Depending on the engine design, it is normal for the oil temperature to be higher tan the coolant. The coolant maximum temperature is restricted by the boiling point of the coolant, so the radiator is designed with excess capacity so that it never boils. The oil has a much higher safe working temperature, so the oil cooler (if there is one) is much smaller.

You should not worry unless the oil temperature is regularly over 150 degrees C.

[ohyes]

Yes guys I was talking about the engine oil temperature! Sorry about that, I was too tired after work yesterday.

Thank you for your answers! I attempted to find an answer in the owners handbook but I failed

Edit: @sticky I've changed the engine oil, box oil not more than 300km ago.

[Paul-R]

You should not worry unless the oil temperature is regularly over 150 degrees C.

On my X7 there are no figures to match the graduations so you have to trust that the dial designers have calibrated them sufficiently accurately too match the percentage the bar moves across.

[Stickyfinger]

Sod the temperature.............I want to panic everyday by watching an Oil Pressure gauge at start-up and wondering every time if it will rise at all.


Oh the good times

[ohyes]

To be more precise, the bars dont appear to be on the same level (coolant and oil) as shown in the picture:

The coolant temp seems to be lower than the engine oil temp

I apologise if this is a stupid question to you, I'm not a specialist in this field

[Stickyfinger]

Nor are Citroen

[ohyes]

So guys today while driving in the morning I was observing the coolant temp (left) and engine oil temp (right). After driving for 30mins after cold startup at 3 degrees of
Celsius in the morning I got:



While driving I noticed how the coolant temp (left) increased to 3 bars, stayed for a while and decreased to 2 bars. After some time it increased again to 3.

So I'm really curious about this so Any thoughts are very welcomed and appreciated.

[Paul-R]

The first thought is that the bars don't actually indicate temperature, they indicate the data that the ECU sends to be displayed. There is no direct connection between the temperature sensors and the gauges, The ECU interprets the data and decides how many bars should be showing and so ultimately depends on what it has been programmed to do.

But, if we accept that the bars actually represent something real, then it's more-or-less as I would accept. The engine heats the oil up first as it's in closer contact with engine and then the water follows. The 2bars - 3 bars - 2bars movement could be an indication that the engine has heated up to the point where the thermostat (Do the engines have a thermostat? Is there now a valve that is under control of the ECU?) has opened and that has reduced the temperature back a slightly lower running temperature.

[ohyes]

The first thought is that the bars don't actually indicate temperature, they indicate the data that the ECU sends to be displayed. There is no direct connection between the temperature sensors and the gauges, The ECU interprets the data and decides how many bars should be showing and so ultimately depends on what it has been programmed to do.

But, if we accept that the bars actually represent something real, then it's more-or-less as I would accept. The engine heats the oil up first as it's in closer contact with engine and then the water follows. The 2bars - 3 bars - 2bars movement could be an indication that the engine has heated up to the point where the thermostat (Do the engines have a thermostat? Is there now a valve that is under control of the ECU?) has opened and that has reduced the temperature back a slightly lower running temperature.

This actually may be the case, not sure if the 1st or 2nd one, but still. Since I haven't noticed any changes in the drive itself. Everything seems as good as before. It's just I was being aware of some early signs of malfunction, but hopefully it is not.

Thank you for your detailed post mate!

[vborovic]

@ ohyes - What you've posted in your picture is perfectly fine ... only after a longer drive will the left indicator come close to the right side one's value

[white exec]

Those visual displays have no units. As such, they are just a graphical representation of normal and abnormal operating conditions. You might as well have a traffic-light system. Can't go bothering today's average driver with figures, can we?!