986 3.2S 60k should I have thicker oil and old tested?
Discussion
I love my car (owned for 3 years) but am worried about the IMS - 60,000 miles seems to be an oft quoted danger time. The clutch was replaced 5,000 miles ago so I am reluctant to have preventative work done. Its due a major service. Should I ask my Indie to put 5w40 oil in? Should I get the oil analysed? Is ther anything else I should do?
Car only does a few thousand miles per year so It gets an annual Mobil 1 oil changes.
Obviously I don't want a £5k engine failure on a £7k car though i could afford it if I had to so I'm minded to take the risk while trying to minimise the risk.
Thanks
Car only does a few thousand miles per year so It gets an annual Mobil 1 oil changes.
Obviously I don't want a £5k engine failure on a £7k car though i could afford it if I had to so I'm minded to take the risk while trying to minimise the risk.
Thanks
nickfrog said:
I would switch to 5w40 indeed, 0w40 very thin. Get you indy to look at the oil and also open the old oil filter for either metal particules or bits of seal.
5W-40 and 0W-40 are the same thickness when hot - both are 40-weight oils. The 5W-40 just thickens-up more as it gets colder. Result? Same protection for your engine when at running temp, 5W-40 less able to get round the engine during really cold (minus lots of centigrade type of cold) starts. Totally pointless change.If you want oil that is thicker during normal running, then you would need to go to a 45/50/55/60 weight oil. There are some 5W-50s around that would do the job. A 5W-50 is thicker than a 5W-40 at running temp but the same thickness as a 5W-40 when cold.
Now for the confusing bit. Remember that if you run a higher viscosity oil (higher at running temp, that is) you will get less flow - volume of oil supplied to the various bits of the engine - for the same pressure. As pressure is limited by the relief valve to a specific value, your engine can't run more pressure to increase the flow back to where it would be with the lower weight oil. Is a slightly thicker oil better than a slightly thinner one that is replenished slightly more quickly by the pump? Also remember that better flow = more frequent trips for the oil through the cooler, so a thinner oil should run a little cooler - which surely negates the purpose of using a thicker oil to start with? Complex stuff!
Edited by Ian_UK1 on Saturday 24th September 17:19
Ian_UK1 said:
5W-40 and 0W-40 are the same thickness when hot - both are 40-weight oils. The 5W-40 just thickens-up more as it gets colder. Result? Same protection for your engine when at running temp, 5W-40 less able to get round the engine during really cold (minus lots of centigrade type of cold) starts. Totally pointless change.
If you want oil that is thicker during normal running, then you would need to go to a 45/50/55/60 weight oil. There are some 5W-50s around that would do the job. A 5W-50 is thicker than a 5W-40 at running temp but the same thickness as a 5W-40 when cold.
Now for the confusing bit. Remember that if you run a higher viscosity oil (higher at running temp, that is) you will get less flow - volume of oil supplied to the various bits of the engine - for the same pressure. As pressure is limited by the relief valve to a specific value, your engine can't run more pressure to increase the flow back to where it would be with the lower weight oil. Is a slightly thicker oil better than a slightly thinner one that is replenished slightly more quickly by the pump? Also remember that better flow = more frequent trips for the oil through the cooler, so a thinner oil should run a little cooler - which surely negates the purpose of using a thicker oil to start with? Complex stuff!
I don't think it is as simple as that - As Baz Hartech has said "I am not tribolgy expert and will not get drawn into arguments about oil - but the idea that oil thickens up when it gets hot is in my experience wrong. I think the claim is that it works as well as higher grade oil when hot - but this doesn't take into account that when bearings wear the lateral clearance is greater so the oil has less resistance to squeezing out the side of shells etc and therefore does not support the bearings as well. Similarly if the oil is a thicker grade it usually is thicker when hot and I have had my amateur ideas discussed with technical oil racing experts from Mobil and Castrol and both agree with my general view."If you want oil that is thicker during normal running, then you would need to go to a 45/50/55/60 weight oil. There are some 5W-50s around that would do the job. A 5W-50 is thicker than a 5W-40 at running temp but the same thickness as a 5W-40 when cold.
Now for the confusing bit. Remember that if you run a higher viscosity oil (higher at running temp, that is) you will get less flow - volume of oil supplied to the various bits of the engine - for the same pressure. As pressure is limited by the relief valve to a specific value, your engine can't run more pressure to increase the flow back to where it would be with the lower weight oil. Is a slightly thicker oil better than a slightly thinner one that is replenished slightly more quickly by the pump? Also remember that better flow = more frequent trips for the oil through the cooler, so a thinner oil should run a little cooler - which surely negates the purpose of using a thicker oil to start with? Complex stuff!
Edited by Ian_UK1 on Saturday 24th September 17:19
I would advocate going for 5w-40 or even 10w-40. The problem is everyone including the experts have very different views about oil - I would stick with the Hartech's advice as they are the ones with most knowledge about these engines. Worth giving them a call and getting advice, I expect you have read the info on the website http://www.hartech.org.uk/
eagle1 said:
I don't think it is as simple as that - As Baz Hartech has said "I am not tribolgy expert and will not get drawn into arguments about oil - but the idea that oil thickens up when it gets hot is in my experience wrong. I think the claim is that it works as well as higher grade oil when hot - but this doesn't take into account that when bearings wear the lateral clearance is greater so the oil has less resistance to squeezing out the side of shells etc and therefore does not support the bearings as well. Similarly if the oil is a thicker grade it usually is thicker when hot and I have had my amateur ideas discussed with technical oil racing experts from Mobil and Castrol and both agree with my general view."
I would advocate going for 5w-40 or even 10w-40. The problem is everyone including the experts have very different views about oil - I would stick with the Hartech's advice as they are the ones with most knowledge about these engines. Worth giving them a call and getting advice, I expect you have read the info on the website http://www.hartech.org.uk/
Oh boy - here we go! The higher number in an oil's multigrade spec defines its viscosity at 100 degrees C. If 2 oils have the same number, then by definition, they will have the same viscosity (thickness) at 100C. Where the idea comes from that an oil with a worse cold-start rating - that thickens up a lot more as it gets cold - will somehow not conform to its running temperature viscosity rating and will offer some extra, mythological engine protection, I have no idea.I would advocate going for 5w-40 or even 10w-40. The problem is everyone including the experts have very different views about oil - I would stick with the Hartech's advice as they are the ones with most knowledge about these engines. Worth giving them a call and getting advice, I expect you have read the info on the website http://www.hartech.org.uk/
If you would like a proper explanation of oil viscosity , please have a read through the page linked-to below. The final graph and numbers is a very simple visual representation of how viscosity varies between differently-rated oils.
http://www.kewengineering.co.uk/Auto_oils/oil_visc...
But what you all should understand is that the way viscosity is measured is not telling you how quickly it will squeeze out through a gap under pressure or load nor how it will squeeze out of an increasingly large gap between a piston and a cylinder bore. It only tells you how quickly it drips through a hole under gravity.
Furthermore the temperature that the oil rised to when in brief contact with hot metal is not the same as just the simplistic flow rate through a cooler - and furthermore it is irrelevant how frequently it flows round an engine if it is changed at the right intervals. If (for a simple example) the cylinder bores have gone oval to say 0.1mm (not uncommon) then when under load the film strength on the thrust side supports the piston and transfers heat but the opposite side may just be a gap so it is impossible to transfer the same amount of heat - the piston gets hotter but doeas the oil (if some of it is not picking up heat? Then again the range of viscosities covered by a grade of oil varies - so those with the least range tend to operate in a smaller range (and therefore if the temperature of the oil goes even higher they do indeed remain thicker. So in this case a 5-40 would have a smaller range than a 0-40 for example.
All these practical considerations mean that it is extremely complex to actually work out exactly what is going on theoretically and this is why development engineers and racing technicians undergo tests and notice the results when they try different oils and grades - and even if they don't fully understand why - they do find out which is best for a given application.
This is why expereinced engine builders (who rely more than anything on feedback over many years to gain the expertise they trade on) have discovered that when an engine is under extra duty - a thicker oil makes it last longer (or when a known fragile engine is put to test - a thicker oil helps it survive longer).
Although I have met engineers that claim a thinner oil produced more power on a dyno (although i never found that) - I have never met any racing engine builder who has found a thinner oil protects a fragile engine better (although there is bound to be an exception along shortly).
This is the problem with amateur contributors who trot out theory and ignore experience - they simply have not attached sufficently complex links to what actually happens - they just follow very basic theory without realising it is more complex than that.
What I have found - during all my working life - is that often the theory does not seem right in practice - until that is you understand that the problem was not the one you thought it was or the way things actually worked was different.
Eventually - when you fully understand the issues - the theory is right - when it is applied to the right issues and subject matter - it is more often the simplistic linking of theory to a misguided view of what is going on inside an engine - that results in the wrong conclusion being pronounced - and this is why it usually flies in the face of those who have simply found out from trial and error - what actually works best - but often without knowing why.
I always prefer to apply whatever experience/trail and error or the combined findings of years of engineering tell me works and then afterwards - I sometimes then find out later why it really works - and still that fits the original theory. Trying to do it the other war around usually simply confuses theory and practice.
Baz
Furthermore the temperature that the oil rised to when in brief contact with hot metal is not the same as just the simplistic flow rate through a cooler - and furthermore it is irrelevant how frequently it flows round an engine if it is changed at the right intervals. If (for a simple example) the cylinder bores have gone oval to say 0.1mm (not uncommon) then when under load the film strength on the thrust side supports the piston and transfers heat but the opposite side may just be a gap so it is impossible to transfer the same amount of heat - the piston gets hotter but doeas the oil (if some of it is not picking up heat? Then again the range of viscosities covered by a grade of oil varies - so those with the least range tend to operate in a smaller range (and therefore if the temperature of the oil goes even higher they do indeed remain thicker. So in this case a 5-40 would have a smaller range than a 0-40 for example.
All these practical considerations mean that it is extremely complex to actually work out exactly what is going on theoretically and this is why development engineers and racing technicians undergo tests and notice the results when they try different oils and grades - and even if they don't fully understand why - they do find out which is best for a given application.
This is why expereinced engine builders (who rely more than anything on feedback over many years to gain the expertise they trade on) have discovered that when an engine is under extra duty - a thicker oil makes it last longer (or when a known fragile engine is put to test - a thicker oil helps it survive longer).
Although I have met engineers that claim a thinner oil produced more power on a dyno (although i never found that) - I have never met any racing engine builder who has found a thinner oil protects a fragile engine better (although there is bound to be an exception along shortly).
This is the problem with amateur contributors who trot out theory and ignore experience - they simply have not attached sufficently complex links to what actually happens - they just follow very basic theory without realising it is more complex than that.
What I have found - during all my working life - is that often the theory does not seem right in practice - until that is you understand that the problem was not the one you thought it was or the way things actually worked was different.
Eventually - when you fully understand the issues - the theory is right - when it is applied to the right issues and subject matter - it is more often the simplistic linking of theory to a misguided view of what is going on inside an engine - that results in the wrong conclusion being pronounced - and this is why it usually flies in the face of those who have simply found out from trial and error - what actually works best - but often without knowing why.
I always prefer to apply whatever experience/trail and error or the combined findings of years of engineering tell me works and then afterwards - I sometimes then find out later why it really works - and still that fits the original theory. Trying to do it the other war around usually simply confuses theory and practice.
Baz
anonymous said:
[redacted]
Thicker oil 'hangs on' better than thinner oil (compare water with oil for example) so all surfaces have a thicker cold film on startup?Ian_UK1 said:
5W-40 less able to get round the engine during really cold (minus lots of centigrade type of cold) starts.
I don't believe we can compare 5w and 0w in this way. We need to consider viscosity @ temp, meaning the ambient temp you start at. There is likely to be overlap between different viscosity oils if the full spectrum is examined.I don't know for certain that running 10/60 in my GT motor is the best thing to do but went along with it after a race engine builder told me 40-weight is too thin.
I regret not having the previous 0/40 tested (allowing comparison with 10/60 in the future) so I would do that.
Ian_UK1 said:
5W-40 and 0W-40 (...) Totally pointless change.
Thanks for the lengthy "lessons" about oil grades and sorry but they were even more pointless. Sometimes it's more helpful to keep things simple instead of coming up with loads of irrelevant facts/data/opinions. This does the job quite nicely:
GT Glee said:
anonymous said:
[redacted]
Thicker oil 'hangs on' better than thinner oil (compare water with oil for example) so all surfaces have a thicker cold film on startup?Alternatively, have a look at LN Eng's site http://www.lnengineering.com/ims.html, they seem to know a thing or two about the M96/M97 engines too...
Edited by nickfrog on Monday 26th September 15:53
Shoestringracer said:
I love my car (owned for 3 years) but am worried about the IMS - 60,000 miles seems to be an oft quoted danger time. The clutch was replaced 5,000 miles ago so I am reluctant to have preventative work done. Its due a major service. Should I ask my Indie to put 5w40 oil in? Should I get the oil analysed? Is ther anything else I should do?
Car only does a few thousand miles per year so It gets an annual Mobil 1 oil changes.
Obviously I don't want a £5k engine failure on a £7k car though i could afford it if I had to so I'm minded to take the risk while trying to minimise the risk.
Thanks
The engine has made it to 60K without any oil related problems. I'd say if the oil you're using and the oil change interval you're following was inadequate you'd know it by know.Car only does a few thousand miles per year so It gets an annual Mobil 1 oil changes.
Obviously I don't want a £5k engine failure on a £7k car though i could afford it if I had to so I'm minded to take the risk while trying to minimise the risk.
Thanks
It if ain't broke don't fix it.
Added: I'm not a big fan of oil additives, but the senior techs I consult with advise for vehicles that are used infrequently, Swepco 502 oil treatment (I had some analyzed: 200ppm molybdenum) is recommended. The additive can help quiet an engine down upon startup. I'm less convinced the additive could do anything once the oil is hot and breaks down. (However, neither tech suggests that it does.)
I have tried some in each of my cars and really I didn't notice any difference. But I drive both of my car cars quite regularly and neither car spends more than a few days (except at very rare intervals when I'm away for a week or more on business or vacation) between starts and usage.
Here's a link:
http://www.swepcousa.com/lubesite/lubesb/J03776_50...
Sincerely,
Rockster.
Edited by Rockster on Monday 26th September 19:17
Edited by Rockster on Monday 26th September 19:32
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