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Well dear supa i would to tell you what mine sits at but i dont have A FOOKIN
OIL TEMP GAUGE along with umpteen other things

its a fookin conspiracy

Hi
Do you mean Oil or Coolant Temp? If your looking at the Gauge on the right of the panel that usually coolant temp otherwise you must have a separate gauge for the oil. But just as a response the oil will run at almost the same as the coolant temp but it depends where the sensor is positioned because the oil drops into the sump with air flowing over it. Anyhow, the running temp of the coolant should be around 90C after fully warmed up and the system should maintain that easily, if it is rising to 110C then I would say you have a developing problem. Diesels run a bit cooler than a petrol because the flash point of the fuel is higher - it takes longer to warm up but is easier to control. Because of this radiators do tend to sludge up a bit quicker. So if you are sure the thermostat is working ok ( you will need to take it out to test it) and the coolant level is being maintained it is likely the radiator needs a specialist to check it out. Note - Both diesel and petrol are regulated at between 80/90C and just because the flash point is higher on diesels it does not mean it will not overheat if not regulated.

I know it's not much use to you Soooops, but on mine both needles point pretty much straight up when she's fully up to temperature, which means that the water is at about 90 and the oil is at about 115ish. I think this is all part of the pug master plan, because the car seems to reach a real comfortable cruising sweet spot when the speedo points straight up at 80 and at that speed in top gear the rev counter points where? yup straight up! Then when the fuel tank is half full you've got a full set

Cheeky Bint!!! That's what I get for trying to help is it?

Anyway we all know that can't be a girl quote 'cos they never look at the dash. How will a girl ever notice that all the needles point straight up at 80 when she's doing her make up in the rear view mirror whilst using a hand held 'phone and smoking?

Hi well I did say it depends on where the sensor is situated because the oil is in direct contact with the hottest parts of the engine and until it gets flung onto the parts that are water cooled and into the sump it will be varying. But on average the heat will be absorbed by the coolant and be about the same value save for the odd burst. It is interesting as you say but what the purpose of it is to the motorist I'm not sure since it can't be altered in any way and as long as you've got plenty of oil in it's an irrelevance. The fact is that the coolant is sufficient unless you are an oil boffin and can monitor the effects of different oils - very interesting. Just another point though - does it have an oil cooler because that may be the reason. You also mention that your water temp fluctuated as well so there may be something going on as well - the oil temp would increase much quicker than the coolant if here was something happening with the coolant -say a dodgy theremostat.

Longintooth wrote:It is interesting as you say but what the purpose of it is to the motorist I'm not sure since it can't be altered in any way and as long as you've got plenty of oil in it's an irrelevance.

Actually it can be altered - either by time or by throttle position.

Firstly, it starts off the bottom of scale when you start the car - so you have a good indicator of when your car is up to running temperature

Also I've discovered that my V6 running flat out (speedo almost pointing straight down) for a reasonable distance (in another country) will make the oil temperature go high enough to persuade you to ease off a bit (and change the oil after), despite the coolant temperature gauge almost being too cold to register

I'd imagine oil burners can get a bit toasty too while towing, and the 2-fan radiator shrouds seem to do an amazing job of keeping temperature steady...

Hi
I'm not saying the oil temp does not vary slightly - on private vehicles and almost all commercial vehicles they don't fit an oil cooler on the engine and I was surprised to learn that Peugeot even fit a temp gauge for the oil. However, because the oil simply drops into a sump with no bespoke cooling system there is no way to control it and it is accepted that overall it will average out to cooling temp. The oil picks up most of the heat from small amounts of oil that contacts the head, bore and pistons which is why the coolant is pumped vigorously around these areas to maintain the average temperature of the engine. Modern oils are designed to withstand high temperatures and remain within the viscosity range recommended by the manufacturer to operate in hot and cold climates.
It is psychically impossible to get the bulk oil temperature higher than the coolant temp first. If you take your car into an MOT test station they will have to run the engine a long while after the coolant temp is up to get the oil temp up so that emission test can be sure its up to temp, this is because there is a small amount of oil flowing around compared to the water coolant so it takes longer to pick up the heat. Otherwise If you think about it logically this would mean that it would be better to have an oil cooler fitted instead of a water coolant system since that would indicate that the oil is doing most of the cooling which it is not simply because it could not cope. So if the coolant temp is above normal the oil temp will average out higher - the oil does act as coolant is a way by reducing the friction of moving parts to prevent seizure and it does get to parts that others can't reach quicker. but friction generates much less heat than the combustion chamber and this can be noted by measuring machines that don't have a combustion element.

Longintooth wrote:Otherwise If you think about it logically this would mean that it would be better to have an oil cooler fitted instead of a water coolant system since that would indicate that the oil is doing most of the cooling which it is not simply because it could not cope.

The V6 really does need one. During normal driving the temperature of the oil is the same as the water - 90 urban, 65 extra-urban. However push it hard and the water temperature will remain low due to mucho airflow through the radiator but the oil's hitting over 140

My friend "won" a V6 VW Sharan ebay special and was concerned at the oil being 108 degrees on the M1 on the way home, an oil change brought that down to 102 degrees

115 seems a tad high for the HDi but I wouldn't say the gauge is so acurate!

I'm glad I haven't got a gauge - out of site out of mind...........

Hi
I'm a bit puzzled and curious about this and I'm not doubting what you say. But if you understand that the water will take the heat away from the areas that get hot and where the oil also contacts then the oil will be about the same temperature as the water. Example if you have a kettle full of water and turn up the heat, the flame in contact with the kettle will be about 600C but the kettle won't get to that temp whilst there is water in the kettle (Trying to talk it down). The oil may vary a bit in the hot contact zones but designers will have worked out that it is within the margins allowed. NOW, this is where many slip up when they start altering the designs - fitting larger turbos, remapping, etc. Any problems that occur become more difficult to identify. Does it have an oil cooler with any kind of thermostat fitted? Is there any chance the block may be silting up with gunge preventing or creating localised hotspots which are pushing up the oil temp - and may be getting near to a seizure say in the lower half of the liners. This area suffers from slow to stationary piston speeds and thus oil sticks around longer so gets hotter before it dribbles off to the sump and is where gunge would pile up.
In this scenario coolant may not be able to get the heat away as quick as it should from hotspots - this said it would be useful to hear from others or someone with knowledge of what this engine oil temp should run at when up to running temp and under high load. You know many manufacturers stopped putting temp gauges in - just little lights that come on if it gets to hot partly to cut costs but also they did not want owners to worry about small fluctuations occurring because the water temperature could theoretically rise to 130C and be ok if it were being run say in high ambient temperatures or at high altitudes. This is because the system is pressurised and won't boil off the water at 100C 14.5 psi (Sea level).

I would say the more worrying aspect is the huge amount of time it takes for the oil to warm up in the first place.

Many times I've "opened up" an engine once the Temp gauge say's it's ok but in reality the oil is probably only 40-50 degrees I think it takes at least 30 minutes of steady running to reach full temp, or, 5 miles on the motorway.

Hi
Welton is correct in what he says for a number of reasons the oil will be thicker when it's cold and increases drag on the oil pump, water does not burn off as quick but as ever there is always a case of either to cold or too hot. The oil temp fluctuates when for example you belt it down the road - the coolant does not rise immediately but the exhaust gasses create heat instantly at the turbo then the oil has a lot of work to do to keep the bearings cool but the oil is so thick it won't flow through quick enough another reason why turbos fail prematurely if it's a regular habit. Good practice let the engine warm up before any hard driving especially in winter.

Hi
With such haphazard diagnostics still around I think I'll be working when I'm 100 or give in with despair.