JET951

Hi floatingkiwi actually the hot oil viscosity( available oil pressure at a given RPM ) between a 5w-50 & say for example a 15w-50 is not the same I have never yet found a 5w-50 that will give the same oil pressure at 100 deg cel ( operating oil temp )as a 15w-50 and particularly a 20w-50 , at 100 to 120 deg cel( 120 deg cel is common on the track ) the 20w-50 will always out perform any 5w-50 in oil pressure available ( same engine , same oil temp , same RPM ) all very simple physics , an average 5w-50 is more like a 5w- 45 & an average 15w-50 is more like a 15w-49

Remember the 944S2 engine feeds its con-rod journals ( big end bearings ) via a "road car compromised design " of radial feed , meaning the faster the crankshaft spins the more the oil feed coming in is wanting to be pushed out via centrifugal forces( faster it goes the worse it gets ) & without enough oil pressure at the centre of crank journals ( 2 & 3 ), 2 & 3 are furthest away to be feed with oil pressure or put another way they are getting whats left of the oil pressure after 1 & 4 are feed

Remember also that the word we use for the white metal con-rod / big end " bearings" is a slightly deceptive word because it gives the impression that its a bearing & makes metal to metal contact( like a ball race bearing ) , but in fact its the oil film & oil pressure between the white metal bearing shell/s and the crank journal is what is actually the bearing . No metal to metal contact is to take place , the oil pressure & the corresponding oil film strength ( last card in the pack ) is all there is between all running well & a spun bearing ( destroyed crank & very possible con-rod letting go completely )= destroyed engine

Now , the low oil viscosity recommendations that do not correspond with whats written in the owners manuals that came with these cars "NEW" is a modern era stuff up ( this alone is an interesting story that I do not have time for here )

Minimum engine oil viscosity at the track we use is 25w-60 & I do mean minimum which means we can & do at times do use higher ( dependant on ambient temps )

Engine Oil in the engine sump not to go over 120 deg cel , which means larger oil cooler/s

For a dedicated 944 track car , be it 944S2 / 951/ 968 etc etc etc , we do not use the way too heavy standard pistons + they are way too old anyway , high quality aftermarket & lighter aftermarket pistons are cheap insurance

For a dedicated 944 track car , be it a 944S2 / 951 / 968 we never ever use the old standard con rods ( way too old )& high quality aftermarket con-rods are cheap insurance

I never discuss oil brands unless its vital & its not vital

Regards
Bruce B

JET951

Hi Wisconsin Joe , many thanks for you're detailed reply , much appreciated

Regards
Bruce B

Ish_944

Dear Bruce,

If you say 5W-50 will not give sufficient warm oil pressure then could you please let us know what oil pressures we should aim for?
I had 1-1.5 bar oil pressure with 15W-40 at idle. 5W-50 gives me 3.5 bars. With 25W-60 I imagine the oil pressure relief valve never actually closes...

BTW, I have an oil pan baffle and an external oil cooler additionally to the stock oil-water heat exchanger.
I also have the "windage ports" as Lindsey Racing calls them. I wonder what you think of these in general and what modifications you would recommend to improve oiling?

Thanks a lot for all the great information!

Ish_944

OK, I wanted to see how true this "5W-50 behaves more like a 5W-45 at operating temperatures" could be. I looked at a few data sheets.

Observations:
XXW-50 oils have ~18 mm2/s viscosity at 40 Celsius.
10W-60 oils have ~23 mm2/s viscosity at 40 Celsius.
The Valvoline 20W-50 is almost a W-60 oil.

My conclusion:
A 5W-50 oil is not inferior to 15W-50 or 20W-50 oils at 100 Celsius.
So imho the topic is more like W-30 & W-40 oils do not have enough shear stability and/or viscosity for our engines at operating temperatures.
Use XXW-50 for the street, XXW-60 for track at hot weather. Choose XX based on your climate. (Although I think getting the lowest possible value there can only help at startup.)

All viscosities in mm2/s at 40 / 100 degrees Celsius.

Liqui Moly
Super Leichtlauf 10W-40 93.7 / 14.0 https://pim.liqui-moly.de/pidoc/P000...40-26.0-en.pdf
Molygen 10W-40 96.3 / 14.8 https://pim.liqui-moly.de/pidoc/P001...40-20.0-en.pdf
Touring High Tech 15W-40 101 / 14.4 https://pim.liqui-moly.de/pidoc/P000...40-32.0-en.pdf
Molygen 5W-50 117 / 18.5 https://pim.liqui-moly.de/pidoc/P000...50-12.0-en.pdf
Molygen 15W-50 133 / 17.5 https://pim.liqui-moly.de/pidoc/P000...50-13.0-en.pdf
Touring High Tech 20W-50 153 / 18.1 https://pim.liqui-moly.de/pidoc/P000...50-27.0-en.pdf
Race Tech GT1 10W-60 168 / 24.0 https://pim.liqui-moly.de/pidoc/P000...60-21.0-en.pdf

Valvoline
VR1 Racing 5W-50 109 / 18.0 https://www.valvolineeurope.com/uploadedFiles/7824.pdf
VR1 Racing 20W-50 193 / 21.1 https://www.valvolineeurope.com/uploadedFiles/8848.pdf
VR1 Racing 10W-60 158 / 23.0 https://www.valvolineeurope.com/uploadedFiles/7825.pdf

Mobil 1
5W-50 108 / 17.5 https://www.mobil.com/english-au/pas...xxmobil-1-5w50
15W-50 125 / 18 https://www.mobil.com/english-us/pas...smobil-1-15w50
15W-50 125 / 17.4 http://www.chemcorp.co.uk/creo_files..._15w50_pdf.pdf

Castrol
GTX 15W-50 145 / 19.1 https://msdspds.castrol.com/bpglis/F...PXE-93YH6W.pdf
Edge 10W-60 SDS 160 / 22.7 https://msdspds.castrol.com/bpglis/F...PXE-9UZHAE.pdf

Motul
300V 15W-50 128.1 / 17.8 http://www.motulshop.nl/docs/datashe...2015W50_GB.pdf

Total
10W-60 167 / 23.6 http://www4.total.fr/asia-oceania/ch...Z%20RACING.pdf

Shell
HX5 20W-50 177.9 / 19.08 http://arizonamotors.ro/userfiles/pr...Amotors.ro.pdf
HX5 SN 20W-50 159.4 / 17.67 https://www.google.at/url?sa=t&rct=j...DsmkehfzGJTEcl
HX3 20W-50 157 / 19.0 http://www.ozgunshell.com/yuklemeler...3%2020W-50.pdf
10W-60 150 / 22.8 https://www.google.at/url?sa=t&rct=j...SOirnbWf9YM3F6

Raceboy

I buy in 2litre metal cans and pay 31 euros for the can. If I buy 20litre one then price would be approximately 20% cheaper per litre.

Regarding price I have never thought that it is too much. When you come from race track and see 2-3bar pressure with hot oil at idle you know why it is worth it Have used many different oils and most of them break down sooner and you just need to change oil in shorter intervals. I still change oil at least once a year or after each 5000 km. Small cost after building 500 hp 16v turbo engine

JET951

Hi Ish 944 ( do you have a first name ? , because its nicer to talk to a human with a name ) , now first of all , you used the word "WARM " , warm is used as the engine oil transitions from cold to HOT operational oil temp , engine operating temp on a race track ( flogging the crap out of for lap after lap ) , the word warm should read = Extremely HOT & as engine oil gets extremely hot , the viscosity thins & thins & the oil pressure drops & drops ( basis physics )

On the road, to have engine oil as only warm means the engine is running way too cold & you need to get the oil temp above the boiling point of water ( 100deg cel / 212F ) at least a few times to evaporate the water that gets in with the oil in every day driving conditions , if the water is not evaporated then it mixes with sulfur ( a combustion by product ) and this creates acids which attacks bearings etc , so as we can see we do not need WARM

25w-60 race oil ( quite common in Australia because of our hot climate ) for last century car engines that are in last century cars going to the track to be flogged , remember the 928 & 944 engine's ( designed by Porsche deep last century ) was developed in the very early 1970's for the common first world engine " multi grade " oil viscosity ( AT THAT TIME ) of 20w-50 & for track conditions you generally realize that the oil temp at the track will go higher & hence why in Australia the Valvoline racing oil we use is not a 20w-50 ( Valvoline do not sell a 20w-50 racing in Australia ) the 25w-60 race does cope better with our high ambient temps

Now Oil Pressure Relief valve and you're comment " does it ever close " ( silly comment and you know it ) at the track were we use a 25w-60 the oil pressure "HOT " normal operational temp ( 100 to 120 deg cel ) }

At idle , the oil pressure relief valve is closed
At 2,000 RPM the oil pressure relief valve is closed
At 3,000 RPM the oil pressure relief valve is closed
At 4,000 RPM the oil pressure relief valve is closed
At 5,000 RPM the oil pressure relief valve is closed
At 6,000 RPM the oil pressure relief valve is closed

Why is it closed , because the Oil Pressure relief valve opens a lot higher than in 0 - 5 Bar gauge on the instrument cluster

In the workshop manual for the 968 engine ( last of the 944 series ) the manual states when checking oil pressure with a separate workshop oil pressure gauge }

Run engine to the oil temp reaches 80 deg cel ( 80 deg cel is the given test temp ) }

A) idle speed oil pressure should be 2.5 Bar or MORE with oil temp at 80 deg cel

B) Run the engine at 4,000 RPM, should be 4.5 Bar or MORE with oil temp at 80 deg cel . I was always interested how the factory said " Or MORE " , you only get" More "with extra viscosity ( simple physics ) , you see in the workshop manual its specifies "More " & not less , if they wanted less , then you run a lower oil viscosity

Note } the Oil Temp of 80 deg cel is for workshop test purposes , we see our normal "Summer" road oil temps at around 100 deg cel with 2 or 3 hours of city driving & at 100 deg cel to 110 deg cel oil temp, the oil viscosity drops quite a bit compared to 80 deg cel = less oil pressure at 100 deg cel and a bit less at 110 deg cel

Note 2 } On the track we regularly see 120 deg cel & even 130+ deg cel , but we try to avoid anything above 120 Deg cel with the use of larger oil cooler/s & air openings etc & naturally 130 deg cel oil temp gives even LOWER OIL PRESSURE = less oil pressure to no 2 & 3 con-rod journals ( big ends ) , we even had one customer a few years ago that drove his track orientated 944S2 with absolute " Red Mist " , meaning he thrashed this thing on the track & it was a warm/hot day & his separate VDO oil temp gauge ( we mount in the center console reading engine sump oil temp) & his reached 145 deg cel , the only reason this engine survived that day with those oil temps an max revs for very long duration's in all gears was due to the correct oil viscosity for the high oil temp & its a high oil film strength engine oil ( 25w-60 racing ), if this engine was on anything else with the same driver it ,same track,same hot conditions the engine would of destroyed itself

Oh , I had a quick look at the Viscosity charts you listed ( I have them too ) and you will notice that the 5w-50 M1 at 100 deg cel is 17.5 & the 20w-50 Val racing is 21.1 , that means at 100 deg cel they do NOT have the same viscosity , just like I said

Regards
Bruce B

40 + years working on Porsche sports cars 6 days a week

floatingkiwi

Would you mind privately PM'ming me your thoughts?

Ish_944

Dear Bruce,

Thanks a lot for your detailed and kind answer!

Right, in my terminology:
Cold: engine water & oil temps below normal operational
Warm: normal operational temps (90 Celsius water, likely more for oil, maybe 100?)
Hot: Above normal operational temps

So I think we agree here.

Well, my comment is not necessarily silly as
1) I recall the oprv opens at 5 bars (could be wrong on this I admit),
2) If I could even get 25W-60 oil here, at say 20 Celsius ambient temperature under normal street driving conditions,
I think the oil would not get hot enough to drop the oil pressure below 5 bars. Hence, the oprv would not close.

Like I wrote in my comment, if you're on a track in a hot climate, use a XXW-60 oil!
But such an oil in Europe would be detrimental. For example, at (basically) every startup lubrication would be terrible for a pretty long time. Obviously, the warming up phase is the most wearing condition, at least for street cars. I'm sure you know this and agree with me.
So I still think that a XXW-50 oil is sufficient for street and occasional track days. Of course, I'd recommend paying close attention to the oil pressure at the track, though.


With a warm engine (i.e. after running 500 km through the country without stopping) I see 3.5 bars at idle and about 4.5 at 4000 rpm with the 5W5-50 oil in it. So obviously more when the oil is only at 80 Celsius.
But this is good information! Now I know I don't ever want to see less than 2.5 bars!

And if you look at these
Liqui Moly 5W-50 --> 18.5
Liqui Moly 15W-50 --> 18.1
Motul 300V 15W-50 --> 17.8
So you'll see that the 5W-50 is more viscous and thus will produce more oil pressure at 100 Celsius then a 15W-50 oil!

Well, this is just a joke. But the point is, these values are very dependent on the manufacturer.

1) I think all the W-50 oils will give you the same oil pressure at normal operating conditions. Except for the Valvoline 20W-50, as I wrote earlier, that one is much more viscous then the rest.
2) Now, take for example: (these are about typical values of viscosities at 40 / 100 Celsius)
5W-50 110 / 18
20W-50 150 / 18
Since the specs call for 18 mm2/s viscosity at 100 Celsius, the 20W-50 oil has to drop more rapidly then a 5W-50. So if we extrapolate this to 120 Celsius, the 5W-50 *should* have a higher viscosity!

Best wishes,
Istvan

JET951

Hi Istvan , nice to meet you with a human name , you will see that I make sure I write things like } at the track we use in our country & our climate 25w-60 , I never say to use it on the road , even though in our hot climate many people do without any issues at all

You have probably noticed , even the Shell HX5 20w-50 has a higher viscosity than the 5w-50 at 100 deg cel , like I keep saying , this is quite normal

And remember , the worst thing to do is to take a last century Porsche to the track with a large variation oil viscosity ( say like a 5w-50 ) always try to keep it a bit tighter like a 20w-50 , I know it doesn't sound like a big difference , but after a 6 high temp heat cycles at the track on the same day the difference in actual viscosity can get more disparaging

If I was taking a 944 ( any ) onto the track where the ambient temp range was minus 10 deg cel to say + 5 deg cel ( cold/ slippery old track day out ) , I would use a 20w-50 racing oil

The other thing that you might find interesting is Oil Film strength & the higher the viscosity ,the higher the oil film strength , this is extremely important for last century Porsche engines , particularly the High Loaded Flat Tappet designed over head cam arrangement , over the last 20 + years we have seen horrible cam lobe wear / lifter face wear on these engines that have been on so called synthetic " low Viscosity " engine oils & at really low kms , where as the same 944 engines on a high oil film strength 20w-50 engine oil with 4 times the kms travelled has no cam wear at all ( This is got me interested in this subject in the first place ) & its about Hydrodynamic Lubrication = Oil Film strength = Oil Viscosity

And where there is No Oil Pressure at all }

Cam Lobes , hydraulic lifter faces , valve guides , timing chain and timing chain sprockets ( 944S,944S2,968 ) , piston skirts to cylinder/s , piston small end bearings , crankshaft thrust bearings , all these get NO oil pressure & Oil Film Strength is vital , and generally speaking on this planet in this universe , the lower the oil viscosity, the lower the oil film strength , all basic physics

Regards
Bruce B

Ish_944

Bruce,

If you notice, I also wrote that XXW-60 sounds reasonable for racing.
I also appreciated your point of using XXW-50 for the road instead of lighter ones.

You have not said anything about cold starts with your preferred oils. Any comments?
Edit: cold = engine at ambient temperature.

While I very much appreciated your insight, I'm still on the opinion that in my climate the 5W-50 oil is a reasonable choice for a street car that occasionally goes to the track.
I'm not a racer, so even on the track the car will not run for periods longer than about 10 minutes. Moreover, I likely cannot stress my car as much as a decent racer could.
So while I'll closely watch my oil pressure, I'll stick to the 5W-50 for now.

Since I do not really drive the car in winter anymore, I will consider switching over to 15W-50 or even to 20W-50 in the future. I'll have a chat with my mechanic.
However, I have the feeling that whatever a 20W-50 would save me in engine wear on the odd days when I get to track the car, will be lost on the other odd days when I even get to start the car...

H.F.B.

Interesting topic. I googled and found a good explanation about oil pressure.
https://www.lubricants.total.com/oil...un-your-engine
again: https://trucksolutions.total.co.uk/-...t-oil-pressure
As I understand it. As long as my oil pressure is within the manufacturers (Porsche) recommended level, you should be on the safe side.

JET951

Hi Istvan , because you do not drive in winter anymore , I think you're idea of a 15w-50 ( for you're country ambient temp ) would be a good idea , most 15w-50 engine oils have decent oil film strength with reasonable ZDDP AW ( Anti Wear ) packages .

While I think of it , in our climate ( Australia ) I / we see only hot engine wear , not engine wear from cold starts , meaning the multitude of last century Porsche engines ( 944 / 928 / 911 cam & rocker faces / valve guides) we have seen in the last 20 or so years with way too excessive cam lobe / lifter face wear that have been on a low viscosity so called synthetic engine oil ( particularly 5w-40 & 10w-40 ) with relatively low kms traveled , BUT by contrast we see the same model Porsche's with much more kms traveled that have been on a high oil film strength 20w-50 and some 15w-50 engine oils with NO cam lobe / lifter face wear at all ( NONE )

Think about it for a moment 944 / 944S/ 944S2 /951/ 968 , 200,000 - 250,000 Kms with No cam lobe / lifter face wear ( none ) , all of these were on 20w-50 & some 15w-50 engine oils with good ZDDP AW packages

But we have seen lots of the same models mentioned above with one third the kms traveled ( 80,000 kms ) traveled and the cams/lifter faces were badly damaged , and all of these were on 5w-40 & some 10w-40 engine oils

So it can not be cold start wear because the ones with no wear have done ( on average ) three times as many cold starts ( so that cold start theory is out the window ) , so what is left ?

Answer } fairly basic , hundreds of thousands of hours of hot engine ( normal operating ) running with the" high loaded" cam lobes slamming at high speed into their respective lifter faces ( lifters held up by two strong valve springs ) Billions & Billions & Billions of rotational times & with an oil in this area has No Oil Pressure to protect these very last century high loaded flat tappet design metal surfaces & with the lower ( this century ) oil viscosities having to use less & less ZDDP AW additive to meet strict emission protocols for this century cars that do not have high loaded flat tappet design OHC , meaning most modern cars engines have roller rockers to compensate for the lower this century low oil film strength engine oils that have to have less last century ZDDP

Less viscosity & lower levels of ZDDP = low oil film strength = high loaded flat tappet design wear

40 + years working own Porsche sports cars & tying to save a few last century Porsche engines from avoidable this century human inspired destruction

Regards
Bruce B

Lizard944

[QUOTE=Ish_944;14731850]

"I'll have a chat with my mechanic."

I'd rather have a chat with my machinist...lol!

odurandina

The op hasn't discussed cold starts nor differentiated between abusive track racing and street + winter driving in all his many oilwar threads over the years.... He lives in the subtropics..... Why would he start now??

1 more thing. 20w50 doesn't even flow particularly well on cool spring and fall mornings.

If i still had my 968 engine, i might have considered getting a heater preheat the 15w50 in cold weather, except that it was 10x easier just to run 0w40.... then later switching to M1 5w50 and 0w50 with even higher levels zinc/phosphorus.

i'd also stay on the thinner M1 15w50 in cooler weather rather than the thicker 15w50s w/ viscosities closer to M1 V-twin 20w50.... Too thick on startups below 45F.

Porsche engineers who recommend the indy shops change w/ 0w40 synthetic for the cold weather must don't know nuthin.

V2Rocket

i don't recall if i posted it in this thread previously, but interestingly normal, off the shelf castrol GTX high mileage 20w50 has 100C viscosity of over 20.