Engine Oil

[333pg333]

ORIGINAL: Copperman05

Yes thats the table I was talking about, thanks. At the bottom Porsche recommends, yes thats right 'Recommends', using 5W-40 oil for all season use, it lists it as a fuel economy oil as it is a synthetic oil which provides less drag and therefore improves fuel economy slightly. This oil is superior to mineral oil, and is a 'high performance oil' porsches words not mine.

5W-40 is the same viscosity as 10w-40 15W-40 20W-40 at working temperature, so it is not like water as you suggest but exactly the same viscosity at working temp as the other oils, the only difference is the cold weather temperature viscosity.

Your assumption that thick oil is better becasue it doesnt drain down into the sump is incorrect and this it not how oils are designed to be used. Thin oils are BETTER at start up because they are thin, thick oils are less effective at low temps, this is common fact. A thin oil is able to be pumped around the engine much quicker at low temps lubricating the engine, a thick oil takes much longer to circulate and therefore more wear occurs. Notice on the graph you have posted that as temperatures get lower the recommended oil viscosities also get lower, I'm not just making this up...

Edd

As far as we can determine, Porsche only ever used the term 'High Performance' oil in one year's manual. The mechanic that I use who is a front engined specialist went through a number of manuals and we couldn't ever find those oils that you favour termed any else but 'Fuel Economy' oils. I think it was a typo personally. []
No, the thick oil doesn't attach itself to the top end just because it's thick, but it does tend to leave much more of a film on the aforementioned parts.

While I agree that in general the temps we see down here are going to be higher than yours, the fact that the Owner's manual suggests usiing 20w/50 down to below freezing is good enough for me. Plus I get the advantages off the extra protection that a 5/w40 is not going to give. It doesn't have to be on the track either. Stop start traffic in Summer will do it. I use a 25w/60 for the track. As far as the graph recommending lower visc oils the lower the ambient temps, well sure, but do you drive your car in temps lower than -10oC?

The overriding factor in our choices are based on how many 944/951 motors we know that have 'blown' and almost all of them have been using lighter visc oils...and that's not just in Australia.

 

[sawood12]

Hang on a second - the chart posted on the first page says that a 20w40 is good between ambient temps between -10 to over 40 degs - I think that just about covers the UK climate and a lower W viscosity is only going to extend that temp range futher into the lower minus temps. On this basis a 5w40 - 15w50 is going to be more than adequate. Also bear in mind that modern fully synthetic oils are more viscously stable relateive to temperature than a 20yr old oil and will last longer - you could probably get away with a 0w30 for a street car. An ester oil is only going to add to the cold start protection capability of the oil - which at the end of the day is the most important feature of an oil as all the wear of an engine occurs in the first 10mins or so over every journey - once the oil is upto temp there is zero wear occuring - so it is all about your ratio of starts to mileage.

A 60 grade is way way too thick for anything other than a race car or a car that is tracked by a very accomplished driver (much like yourself Pat!!) who will be able to get the oil temps high enough for the 60 grade to reduce to an effective 40ish.

 

[944Turbo]

15W50 for me and my car gets driven hard on road and track (though not managed it for a while), we never see temps as low as -10 in the south though. Oil pressure very very rarely drops to 3.0 bar even at idle on trackdays. Silkolene ProR or mobil 1 motorsport are my preferred oil, though currently trying a millers motorsport.
Castrol magnatec is not magnetic so why shouldn't it stick to Alusil as well as it sticks to anything else - wouldn't use it myself though.
Tony

 

[944Turbo]

ORIGINAL: sawood12

]Hang on a second - the chart posted on the first page says that a 20w40 is good between ambient temps between -10 to over 40 degs - I think that just about covers the UK climate and a lower W viscosity is only going to extend that temp range futher into the lower minus temps

.


Yes but on track or a hard run you are going to get the engine very hot - it is accepted the oil cooler is slightly marginal, so you will get more heat than planned, I prefer the extra protection at the top end of the range.

Tony

 

[Neil Haughey]

15W-50 Mobil 1 for me in the S2 for the past few years and 10W-40 Mobil S in the 968. TBH the thinner oil in the 968 is noticeable as in cold weather the S2 seems slower to crank over, it was faster when I ran it on thinner oil. Main thing for me is I seem to suffer less oil loss in the S2 with the thicker oil. That engine has done over 170K miles though. The 968 is used all year round so for me the cheaper Mobil S makes sense as I changed it recently and will change again at the end of winter.

For the season next year I will probably buy a job lot of the valvoline VR-1 race oil, the stuff with the very high ZDDP content, linky:

http://forums.pelicanparts.com/porsche-911-technical-forum/459139-zddp-notice-vavoline.html

 

[Copperman05]

ORIGINAL: 333pg333

I think it was a typo personally. []

Come on its not a typo stop bending the facts to suit your argument, these oils Porsche talk about are fully synthetic oils, they are called high performance oils because synthetic oils ARE high performance oils. Its that easy!!

Edd

 

[Copperman05]

For what its worth, I run 5W-40 in my S2 and I get 3.5 bar at warm idle, the engine uses very little oil (I dont need to top up between servicing) the engine does not leak and the seals are just fine.

Granted it is fairly low mileage for the age at 97,000 which may a help but I run 5W-40 in my car as it offers the best balance of protection for the type of use it gets. It seems to me that soemone writes an article regarding oil and viscosity and it becomes a bible everyone hangs on every word when in reality its not 100% accurate. There are alot of myths regarding oil, sorting the truth from fiction is not easy.

Edd

 

[333pg333]

ORIGINAL: Copperman05

ORIGINAL: 333pg333

I think it was a typo personally. []

Come on its not a typo stop bending the facts to suit your argument, these oils Porsche talk about are fully synthetic oils, they are called high performance oils because synthetic oils ARE high performance oils. Its that easy!!

Edd

Not bending any facts. Seems like you're the only one who is getting bent out of shape re this discussion. The FACT that in a multitude of front engine Owner's manuals they clearly state your favoured oils as 'Fuel Economy Oils' seems to elude you. As far as them being High Performance oils, well I'm not sure on your definition of a H.P.O., but you won't find race cars using this weight oil, especially 944/951 race cars. Of course it's up to you what you use and in certain cases I don't see any real harm in an English environment based on certain driving habits, but I can only be guided by people that know a hell of a lot more than you or I. In other words, experts. You clearly have your beliefs and more power to you, but to suggest I'm skewing the facts to suit my point of view is untrue.
As for myths surrounding oils, that's correct. The marketing depts of not only the oil companies but also the car companies are largely to blame. The fact that everyone seemed to be sucked into the M1 myth and they reduced their levels of ZDDP without telling anyone is a case in point. They seem to be addressing this problem recently. Probably due to the amount of backlash they were receiving in the marketplace. Many engines were showing high rates of excessive wear or worse. Many mechanics were moving to other brands yet there will always be people that are swayed by the millions of dollars poured into the marketing of said product and refuse to see the truth.

 

[333pg333]

ORIGINAL: sawood12

Hang on a second - the chart posted on the first page says that a 20w40 is good between ambient temps between -10 to over 40 degs - I think that just about covers the UK climate and a lower W viscosity is only going to extend that temp range futher into the lower minus temps. On this basis a 5w40 - 15w50 is going to be more than adequate. Also bear in mind that modern fully synthetic oils are more viscously stable relateive to temperature than a 20yr old oil and will last longer - you could probably get away with a 0w30 for a street car. An ester oil is only going to add to the cold start protection capability of the oil - which at the end of the day is the most important feature of an oil as all the wear of an engine occurs in the first 10mins or so over every journey - once the oil is upto temp there is zero wear occuring - so it is all about your ratio of starts to mileage.

A 60 grade is way way too thick for anything other than a race car or a car that is tracked by a very accomplished driver (much like yourself Pat!!) who will be able to get the oil temps high enough for the 60 grade to reduce to an effective 40ish.

Exactly. At least you're starting with a base W of 40.

 

[Copperman05]

ORIGINAL: 333pg333

but you won't find race cars using this weight oil,

No? Some use an even thinner oil http://www.eurotuner.com/news/eurp_0909_mobil_1_synthetic_racing_oil/index.html

The W in 5W-40 indicates the oils winter abiility, W= Winter. The 5W is measure of how thick the oil is when cold (winter) usually down to -30. The 40 accounts for how thick or thin the oil is at working temperature.

Edd

 

[333pg333]

To "accurately" paraphrase myself...."but you won't find race cars using this weight oil, especially 944/951 race cars.".

You clearly have your preferences. By all means use M1 5w/40. In fact why don't you use 0w/30 based on your logic? You obviously know better than people with a collective experience in real world applications of well over 50 years. So go for it. [] LOL

Oh, and just by the by...there is no such thing as a totally 100% synthetic oil made for general car usage. They all have root stock derived from an organic compound.

 

[sawood12]

at 100 degrees C a 20W40 has exactly the same viscosity and properties as a 0W40 5W40, 10W40, 15W40 etc. The higher the W rating the thicker the oil is at cold temperatures, the lower the number being thinner cold temp viscosity.

Porsche obviously designed the engine to use an oil of around 40 viscosity at full operating temp and the reason for using a higher grade oil in warmer climates is because the viscosity of the oil decreases with temperature therefore in warmer climates and therefore higher oil temps you need to compensate for the thinning by increasing viscosity such that at operating temp you are achieving a viscosity of around 40. This is also true of race cars where the higher operating temps require a higher viscosity to compensate.

At the end of the day modern cars use a 30 grade oil. Now when you've got two surfaces in contact and sliding past eachother then that situation is no different in a 944 engine vs a modern cars engine. Modern synthetic oils have developed such that a thinner oil can offer adequate lubrication between two sliding surfaces at a lower 30 viscosity without being 'squeezed' out from between the surfaces, so in a way a 944 might very well run perfectly happily on a modern fully synthetic 0w30 oil. If this is the case then the cars would benefit from lower drag due to the thinner oil, better flow of oil and more efficient cooling of the engine internals. I think the oil pump may be the only component here that might have a problem as oil pumps often require the fluid to have a certain viscosity to work. Would be nice if you could modify the oil pump to work with the lower viscosities.

 

[Hilux]

at 100 degrees C a 20W40 has exactly the same viscosity and properties as a 0W40 5W40, 10W40, 15W40 etc. The higher the W rating the thicker the oil is at cold temperatures, the lower the number being thinner cold temp viscosity.

Porsche obviously designed the engine to use an oil of around 40 viscosity at full operating temp and the reason for using a higher grade oil in warmer climates is because the viscosity of the oil decreases with temperature therefore in warmer climates and therefore higher oil temps you need to compensate for the thinning by increasing viscosity such that at operating temp you are achieving a viscosity of around 40. This is also true of race cars where the higher operating temps require a higher viscosity to compensate.

At the end of the day modern cars use a 30 grade oil. Now when you've got two surfaces in contact and sliding past eachother then that situation is no different in a 944 engine vs a modern cars engine. Modern synthetic oils have developed such that a thinner oil can offer adequate lubrication between two sliding surfaces at a lower 30 viscosity without being 'squeezed' out from between the surfaces, so in a way a 944 might very well run perfectly happily on a modern fully synthetic 0w30 oil. If this is the case then the cars would benefit from lower drag due to the thinner oil, better flow of oil and more efficient cooling of the engine internals. I think the oil pump may be the only component here that might have a problem as oil pumps often require the fluid to have a certain viscosity to work. Would be nice if you could modify the oil pump to work with the lower viscosities

Good points, well made.

Its the operating temperature of the oil thats key which is why exceeding max oil temps is to avoided, however too thin an oil in a worn engine and the pump will not cope very quickly for the excess volume that passes drops the pressure.

People do not realise how little pressure is needed at the crank to keep it all going for its volume, not pressure that counts as the oils secondary purpose at the crank is to remove heat (note the need for oil sprays also in some cars) and at the cams is more to lubricate although heat is generated.

As for the start up benefits then I think we all need to stand back and consider what these engines managed on when running in when new. A completely different set of oil was available, primarily mineral and thicker than modern oils so I would err on the side of a thicker oil myself. Especially if the engine has a few miles on it.

Modern engines are almost fully blueprinted with manufacturing tolerances manufacturers of yesteryear could only dream about and reserved for handbuild specialist engines hence they will thrive on lower viscosity oils with higher pump pressures to maintain volume and take heat away and consequently lower operating temperatures for longevity between changes.

Summary, thicker wins it for me every time simply due to tolerances and wear for it promotes good pressure and volume. Gauges are notoriously inaccurate by the way unless you buy a good one with an accurate sender prefectly matched. The best are direct ie: wet fed to the gauge.

Also if the gauge wasnt there and you only had a warning light then this thread wouldnt have taken place I`ll bet. Gauges create more to worry about. []

S`wat I say anyway................................discuss...............................[]

 

[sawood12]

Mmm, I really don't think manufacturing tolerances come into it. The only reason why oil has to have any viscosity at all is to prevent it being squeezed out from between surfaces which are in contact and sliding past one another. There is no tolerance between surfaces that are in contact with one another no matter how old the engine, and if there is a clearance then there is no need for lubrication at all. The one and only benefit that viscosity brings to the party is to prevent the oil from being squeezed out - I think it is called shear strength or something like that, in all other respects viscosity is bad - it restricts flow, increases drag, it reduces cooling, it clogs up the engine as it breaks down with age and chemical attack and reduces efficiency. The reason why oils are thinner in modern cars is because oil technology has moved on and provided us with oils at lower viscosities with good shear properties. Cams and cranks havn't changed much in 20yrs - they're still case hardened, drop forged steel based alloys, but oil technologies have moved on significantly.

I take back my comment about a 944 enigne probably being able to run on a modern 30 grade oil. A problem with this is that stable oil pressure, and therefore flow, might not be sustainable. Oil pressure isn't generated by the pump - it is generated by the rotation of the engine parts drawing the oil through the engine. The oil pump is basically a scavange pump to suck up oil from the sump and feed the engine. So at the design stages the engine's oil ways will have to have been designed with a specific oil viscosity in mind and if you go too thin then that will effect the way the oil is drawn through the engine and oil flow may be unstable and reduced - as it will if you go too thick.

Our engines are thriving with many well into the 100k miles and some into 200k miles + with no engine rebuilds. Even the venerable air cooled 911 engines seem to need fairly regular rebuilds judging from the number of 911's for sale advertised as having had a rebuild at relatively low miles, so in anyones book that aint bad. Generally these things havn't been running on thicker than recommended oil grades and i'm sure alot of them have been abused with respect to the oil change interval at some stage in their pasts so i'm not even sure how sensitive the engines are to oil viscosities, within a reasonable band. I really don't think all this worry about oil viscosity is really that essential. Lets all just use decent quality oils at Porsche recommended oil grades and get on with our lives!!

 

[Hilux]

There is no tolerance between surfaces that are in contact with one another no matter how old the engine, and if there is a clearance then there is no need for lubrication at all.

???????????

Of course engines are built to tolerances. It is the tolerances that allow oil to pass through thereby ensuring direct contact between surfaces is avoided. Bearings and journals have agreed tolerances. Piston rings have tighter tolerances to avoid this instead relying on the oil film and smooth hardness to reduce friction.

Oil pressure isn't generated by the pump - it is generated by the rotation of the engine parts drawing the oil through the engine.

???????????????????????

In which case the pressure reading would be a negative! There is no aspect of the engine that would create a negative (suction) pressure. Without head (positive) pressure the oil wouldn't travel anywhere. The only negative pressure in an engine is gravity. The forces upon a journal or bearing squish the oil out, without positive pressure it cannot be replenished.

 

[tr7v8]

ORIGINAL: 333pg333

Curious how significant the supposed charged particles in Magnatec cling to our Alusil cylinders?
I'm in agreement with Thom. I wouldn't put a 10w/40 anywhere near my engine let alone a 5w/40.
Remember that the Porsche manual recommends a mineral based Multigrade oil of 20w/50 down to below freezing temps (-10oC)...and this was on cars as recent as some 996 models.

For those of you that really care about what you put in your engine, here is a most excellent and detailed thread that is relevant to our 'flat tappet' motors. One of the main contributors on this topic, Charles Navarro is a leading expert in this field. I have saved this thread and return to it semi regularly.

http://forums.pelicanparts.com/porsche-911-technical-forum/367300-ultimate-motor-oil-thread-why-we-hate-cj4-sm-oils.html

http://tinyurl.com/yzrxn2t

Funny enough he recommends Added 9/22/2007 Valvoline VR-1 20W-50 -it is marked "Non-Street Legal".And that is what I run, in my 2.5N/A bought in 4 x 5L from my local guy it is 12.50GBP per 5L

 

[333pg333]

The VR1 is an excellent choice.

 

[Copperman05]

I'm sure it is, they do a 10W-30 fully synth version too, or is that a typo?

Edd

 

[333pg333]

ORIGINAL: Copperman05

I'm sure it is, they do a 10W-30 fully synth version too, or is that a typo?

Edd

Nothing wrong with a 10w/30 in the correct or suitable applications. Just not on our Flat Tappet designed motors from the 80's.
Funny how we were reading about a lot of advanced engine wear in UK 944s and 911s in British magazines a few years ago. Guess they must have all been using VR1 20w/50 and the thicker oil created a lot of premature engine wear.

 

[Neil Haughey]

Aussie sarcasm at its best mate []. I agree I think a few ppl have made the mistake of running oils like the old 0w Mobil 1.

The thing ppl don't understand about driving in the UK is that our climate is more or less irrelevant. If you live in or near one of the cities the car could be spending much of its life sat in traffic jams. I drove almost 3 hours in London traffic Friday last and the result was my car broke down from a heat related illness (burned plug lead for starters, may have overheated autobox). In these circumstances where the fan is constantly on/off for hours at end I bet the heat build up under the bonnet is far higher then blasting across the outback, AND with a decent amount of rpm on the motor at least the oil pressure is reasonable rather then spending hours bobbing around 2 or 3 bar. My dad drove busses for many years and he tells me they often had breakdowns caused by the transmission overheating in traffic. If you guys recall the reason I originally switched to Mobil 15w-50 was because I spent a lot of time in traffic (south coast + summer = traffic nightmare) and I was loosing to much oil on 10w-40 oil, switched to 15w-50 and the loss more or less went to 0. OK this is on a 150+K miles motor but then most of our cars are high mileage motors now.