Synthetic oil thermal breakdown?

[Error404]

Did a day at Silverstone yesterday in the coupe, first time on the circuit for me and it was excellent.

During the morning I'd be running pretty consistent and stable 130-135deg oil temps over around 20-25 minutes on track. As the day went on the oil seemed to be less temperature stable and would heat up faster and temperatures would climb steadily over a 15-20 minute session up towards 150deg.
I was keeping an eye on it and backed off to let it cool back down when it started to get up to 150deg. At the end of the day within around 3 laps I was having to back off at the oil temp would rocket to 150deg and oil pressure began become unstable to.
I called it a day at this point and on the drive home (motorway cruising) oil temp would sit at around 120deg whereas I normally expect to see around 100deg. Oil pressure was also 3.5bar not the usual 5 bar. Currently running 10w50 Fuchs Pro Race and have a 19row Mocal oil cooler in the aux rad position.


I assume the oil has been chemically altered by the heat cycling and its viscosity has changed - anyone have any technical information on this kind of thermal breakdown?

[SteveH]

I would have a thought a decent synth oil would be able to cope with temps like yours without deteriorating so quickly. Only way to really prove it was the oil, would be drain and refill during the day and see if that clears the issue. Can't say I noticed high temps at Combe and I was ragging my motor. Not for as long, but certainly driving the motor hard. Do you have an EGT sensor to see what sort of temps you are generating?

[Rusty]

Sounds like the oil thermostat may be worth a check?

Mine sits at 130 all day in air temps up to 30deg.

Could also be head gasket so check compression.

Have you got aany mods to the oil system? Track tyres and hard cornering can mean you'd lose a chunk of oil over a day on track.

Silverstone is on the to do list, was it one of their winter bargains?

[mike74]

I agree with SteveH. Any decent synthetic oil should be good enough for the temps you're seeing I would've of thought. I wonder if you've somehow damaged the oil temp/pressure sender under the oil pump? Another slightly more perplexing suggestion could be that the oil has been contaminated with fuel, which has 'thinned' it slightly. Is it still doing this lower oil pressure thing or has it recovered after a couple of days?

[Rusty]

Oil drain time and cut open the oil filter. I run magnets on mine to help with any debris collection.

[s2driveruk]

good tip re the magnets....got a pic?

[SteveH]

What do most folk do when they are doing an oil change with a large, remotely mounted oil cooler? I'd have to manually drain mine and refill with fresh oil to avoid leaving 1/2 litre of used oil in the system.

[RichLV]

What do most folk do when they are doing an oil change with a large, remotely mounted oil cooler? I'd have to manually drain mine and refill with fresh oil to avoid leaving 1/2 litre of used oil in the system.

Same. But I don't refill it manually. Just drain, and let the oil pump do the work afterwards.

[Error404]

I'm running the stock breather system which obviously returns and oil levels were fine and checked periodically through-out the day.
No EGT but the K24 does generate some heat, and being a journal turbo i guess it will load the oil quite a bit compared to a larger turbo being given an easier life, or a BB turbo.

I did wonder if the oil was contaminated with fuel but without massive blow-by I couldn't really see how with track driving? Car wasn't down on power or missfiring so I can't see that it was running excessively rich and I've not got any codes to indicate lambda outside of the trim range.

I guess an earth or wiring fault on the gauge cluster is a possibility but seems unlikely to me. Car is coming off the road now for winter and a shed load of changes. Two being 0-5v oil temp and pressure sensors to log whats going on through the MaxxECU, I'm also going to fit a fuel pressure sensor.
Will also be doing a load of work to the oil system - I've built a baffled sump with oil control flaps, a decent breather system is in progress and I'm going to try a Mocal thermostatic take-off plate instead of the OE thermostat housing as I'm convinced it's not opening fully or simply doesn't flow enough when it does.
I can't rule out problem with the oil system or a bearing excessively worn. I will check the oil pump and bearings when the sump comes off.



Silverstone was awesome though and is a great circuit for the coupe with the fast sweeping corners. My car was the least valuable machine there to the tune of around £20k Wall to wall GT-Rs & 911s. Some interesting stuff too - a Huracán GT3 racer, 458 Challenge & an NSX Type R and a very lovey Evora GT4.

The old shed feels excellent though with the current set-up, the balance is perfect. Very neutral, the front & rear axle will break away at the same time very predictably and balance very nicely on the throttle. It is a real giggle to drive at the limit and inspires total confidence and so I was able to mix it with some much faster cars. Still pushes a tad on the hairpins but that is the nature of the beast I think.

[Rikki Kitto]

I need to do a track day😜

[steve briance]

How old is the oil? I've previously noticed a drop in pressure on oil nearing its time. It could be as much as 0.5-0.7 bar but that comes back with the fresh oil. Something happens to the oil over time and it def doesn't handle heat as well when it happens!

[mac2226]

Did a day at Silverstone yesterday in the coupe, first time on the circuit for me and it was excellent.

During the morning I'd be running pretty consistent and stable 130-135deg oil temps over around 20-25 minutes on track. As the day went on the oil seemed to be less temperature stable and would heat up faster and temperatures would climb steadily over a 15-20 minute session up towards 150deg.
I was keeping an eye on it and backed off to let it cool back down when it started to get up to 150deg. At the end of the day within around 3 laps I was having to back off at the oil temp would rocket to 150deg and oil pressure began become unstable to.
I called it a day at this point and on the drive home (motorway cruising) oil temp would sit at around 120deg whereas I normally expect to see around 100deg. Oil pressure was also 3.5bar not the usual 5 bar. Currently running 10w50 Fuchs Pro Race and have a 19row Mocal oil cooler in the aux rad position.


I assume the oil has been chemically altered by the heat cycling and its viscosity has changed - anyone have any technical information on this kind of thermal breakdown?

I think oxidation happens because of heat,what your experiencing with oil pressure drop I wouldn't worry too much just change oil again for some fresh oil 👍🏻 And have you used motul 300v this oil is very good for track days my friend uses this on his track cars

[Error404]

Oil is not that old, maybe 2k mikes, but most of them have been fast road and 2 days on track - the car is just a toy so only really gets ragged about
Going to drop some new oil in this week.

[mac2226]

Oil is not that old, maybe 2k mikes, but most of them have been fast road and 2 days on track - the car is just a toy so only really gets ragged about
Going to drop some new oil in this week.

Haha don't blame you alex I would as well

[Thuppu]

Oil temp should not rise to 150C with such big oil cooler. Maybe your thermostat is stuck or you don't get air flow to the cooler..?