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MG MGF Technical - Oil Temperature

I've drive a TF160 which is fitted with an oil cooler, why then does the oil temp appear very similar, if not the same as my previous car MY2000 1.8mpi?

I read somewhere on the BBS that the TF/Oil Cooler combo should be approx 80 deg, whilst the TF shows a temp around 100-110, going up to 120 if under high revs etc..



Try bringing the speed down to around the 100mph mark - that should make it better:-)

Seriously I don't think that 100 to 120 is anything to worry about, I can get up above 130 when doing a long fast stint on the Autobahns!

Ted Newman

I had the temp up to 140deg on the nurburgring last sunday and it didn't do any harm carry on driving fast. I did however pause it for 10 min afterwards and let it idle till it cam down to about 100.

Jorg 10w40 Helix
Jorg Mendgen

Dave - I agree that is indeed odd, as I would have expected a similar oil and water temperature - which should mean oil temperatures of 80 - 90 deg given the opening temperature of the thermostat.

Needs further investigation - not that there is a problem with your car - it maybe that:

1. The water/oil cooler is underspecified for the job and isn't cooling the oil sufficiently - nice work MGR - NOT >:o(
2. The oil temperature guage is giving a more reliable indication of water temperature than the water temperature guage!

As I say, this needs more investigation...
Rob Bell

> The oil temperature guage is giving a more reliable indication of water temperature than the water temperature guage!
note: the water Temp guage is not calibrated, but clamped by the thermostat @88 degrees
but the thermostat is on the 'cold' side of the water system and the oil cooler is probebly on the 'hot' side of the system, thus the oil will cool only to the temp of the water after going thru the 'hot' head.
Even so Daves system sounds wrong because it is giving him readings the same as the F - how is the oil plumbed in? does it have a thermostat?

Will Munns

So what is the thermal gardient across the engine? I can't believe it is up to 40C! Besides, we know from Simon Scutham's experience (if we take his word for it, and frankly, I see no reason why we shouldn't) using a large Mocal water/oil heat exchanger and a remote thermostat, that the oil and water temps are equal (remember that the Elise Stack instrument pack has calibrated digital read outs for temperature rather than a damped mechanical guage as we have).

From Dieter's sensor information page ( we see that the water temperature guage has a huge range of temperature in which the needle will be reading 'normal' (1/3 - 1/2 way around the guage - 65 - 110C). To get the guage up to the red zone, the water temperature has to be 125C.

Not too, that the oil cooler, I suspect, is plumbed into the same side of the engine as the water temperature guage. So IF the oil cooler is working correctly, oil temperature cannot exceed 110C

So why is Dave seeing up to 120C on his oil temperature guage? Are we looking at oil temperature before it enters the oil cooler?
Rob Bell

Sorry I think your maths is a bit screwy it's 30 degrees accross the block (water temp should be minimum 90 degrees if the radiator is in circuit)
Where is the water temp gauge in the circuit- before or after the thermostat?
If the oil gauge is 10 degrees out as well then all is as expected except
I beleive there is a problem because I would expect little movement in oil temp - the real test would be how quickly does the oil *cool* when the engine is no longer under load, on my F it is quite slow, on the TF160 I would expect it to happen a lot faster.

Will Munns

>>Sorry I think your maths is a bit screwy it's 30 degrees accross the block<<

LOL - I was exaggerating the point, sorry ;o)

point is that there is a potentially large difference in the temperatures being recorded by the oil and water temperature sensors.

The water temperature sensor is on the water outlet from the head (left hand side of the engine, front of the block - best seen in pictures A and B on

The oil temperature sensor - not quite sure as to the exact location from dieter's picture (, but I am guessing that it is from the oil filter adapter plate?

Both are a long way from the water thermostat, and indeed from each other.

At no point does water temperature reach 130C - although it would seem that oil temperature is approaching this at times (Dave?).

I think you make an excellent point regarding the rate at which the oil temp falls towards the water temp. Equally it would be interesting to hear how quickly the oil temp warms up towards water temp (on my 1.8i, there is a significant lag between water temp and oil temp reaching 80-90C).

BUT if oil and water temperatures significantly divergent to the tune of 20-30C under heavy loads, then clearly the water/oil heat exchanger is too small?

One of the benefits of fitting an oil changer would be to equalise the temperature gradient across the head and block as the head is primarily water cooled, whilst the block is primarily oil cooled. With what Dave is reporting, this potentially HGF sparing benefit is not being realised.

(Ah - I love these threads - they really make you think on a slow afternoon! ;o)
Rob Bell

Thanks for the input guys, interesting theories?

Oil cool down does appear much quicker than 1.8mpi, although it takes 8-10 mins to reach 110 deg, which I presume would be the "normal" operating temp for the VVC? I would've expected an lower operating temp given the fact that there's an oil cooler, supposedly cooling the oil!!

I'm hoping the most plausible explanation would be, for the oil sensor to be located on the oil outlet feed to the cooler? ie. the hottest oil temp exiting the engine, travelling to the front of the car passing through the cooler. and then back around the nearside.

I'm a bit concerned that there's 100 deg oil circumnavigating the car, I hope the hoses are good quality?

I know Paul Lathwell & Mike Williams have both got the 160, so it would be intersting to see if they've had similar readings?? I hope.

>>I'm a bit concerned that there's 100 deg oil circumnavigating the car, I hope the hoses are good quality?<<

Don't worry Dave, the cooler is located on the back of the engine, rather than upfront with the radiator - so no worries there.

I agree, it would be useful to hear what other TF160 owners experiences are.

Hmm, Will, thinking about the relative temperatures of the water and oil. If we take the asertion that the block is oil cooled, and the head is water cooled, then this makes the sensor readings quite interesting. Both are situated where both the water temp and the oil temp is presumably at their highest (?) - and therefore, most representative of the average head and block temperatures respectively.

Therefore, if the oil temperature guage is reading say 120, whereas the water temperature guage is reading <110, then you are looking at a temperature gradient of up up 20C across the head and the block - which is purely dependent on the load and running conditions of the engine.

Surely this is not a good thing? Presumably this is a phenomenon that is going to be far worse in MGFs where there is no oil cooler to reduce the delta change and therefore the relative expansion of block and head?

FWIW my 1.8i very infrequently shows oil temperatures greater than 120 - most usually in the 90 or so range - ie not that different from the water temperature. I've not had a HGF in 6.5 years and 62k miles. I wonder if the lower oil temperatures that my car is 'used to' has preserved my head?

Suggests an interesting hypothesis doesn't it? That cars that regularly have far hotter oil are much more prone to HGF than cars that do not...
Rob Bell


I don't think there is anything to worry about with regards to oil temperature, mine sits at about the same as yours and I believe Sue's is the same. :)
Paul Lathwell

Hi all,
several good points raised - looking forward to see what real benefit there is of the water/oil-cooler on the TF160 and also the routing of the inlet/outlet... I think it is vital to note that the point where the oil-temp. is measured is just after it has been sucked up in the sump ! And this is supposed to be the coolest part of the whole oil-system. After the oil has passed the pump/filter/ temp-sensor it starts itīs tough job of lubricating and cooling until it enters down to the sump again. And surely the oil has picked up a few degrees during that trip !
Especially Robīs notes on different working oil temps on different cars is interesting. See my comments on the cooling thread that my car despite all those trackdays /sprints etc. never shows any abnormal oil temp. And that not even before the re-work of the cooling system...
A good opportunity to chech the onboard oiltemp readout would be to compare to the reading taken in the sump when going thru a MoT. Hopefully their instruments are well calibrated and spot on ;)

Regards , Carl.

Carl, it would be very interesting to measure oil temperature at various points in the circuit to see how oil temperature broadly alters, and to see whether the location of the oil temp sensor gives a representative reading of global oil temperature.

It would also be useful to see how the block temperature varies - and whether this closely correlates with measured oil temperature - perhaps one of those laser based surface temperature measurement systems would be good for this?
Rob Bell

Has anybody fitted an oil cooler to there MGF!
or a water levle sender?
Ken Spence

Some other readings from a TF160 :-) and previously a 98 VVC (TTB and K&N)

On normal driving (traffic and up to 70ish) then the oil gets to about 100/105. The F was usually at 85-90.

At higher speeds and sustaned (15mins or so) at 85-90MPH (theroretical of course) the TF gets to the 120 mark whereas the F was 100-105.

So if all else is the same I would say the oil cooler doesn't help much but then I seem to remember the 2000MY and later (and I assume TF) oil guages read higher.

As a side note after a higher speed run I usually try to let the oil cool down (by slower driving) as I get nearer the destination, but have found the TF to take longer to cool (relativly) than the F did.

Any thoughts?



Thanks for the info,
as you can see I live in Austria and travel in Germany often were I drive 140, 170 with my MGF and cannot seem to consentrate on driving when I see the water and the oil gauge so high!I would do almost anything to hvae peace of mind. I will drive to England next week to one of the MGF places were I can get a oil cooler because 1% of cooling is better than nothing! what du you think Paul?
Paul, have you heard of the water censor that is on the market now?

Speak to you later.

Ken Spence

Trophy 160 2001
My oil temp @ 70-80 mph run reads 120
Kev .C

This thread was discussed between 20/06/2002 and 23/06/2002

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