Henry964

I really can´t tell why the oil I am using today is used less than the one before, maybe it is because the new oil is heavily additivated (Mos2 and others) and it is also a semisyntethic oil vs a full synthetic, I also spended a lot of money changing gaskets and such to make sure the oil doesn´t leak

evoderby

To start of with, your newly stated oil pressures look to be much more of where they should be on a healthy engine. And yes my car idles with a rock solid 2Bar when hot (not warm, hot) and the end of the scale when cold, my engine has done only 20K miles and runs on 10W60 full synth.

Oil pressure is a result of flow volume from the pump and resistance to flow through the engine. Smaller flow passages provide more resistance to flow (higher pressure). Larger passages provide less resistance, resulting in lower oil pressure. This is why worn out bearings result in low(er) oil pressure. Minimum system pressure is determined by how slow the engine idles and the condition of the bearings. Larger clearances result in more oil leakage from the bearings.

This is why manufacturers such as Porsche are able to state minimum required oil pressure at different rev ranges.

As far as links are concerned there are so many on sites like Bobistheoilguy. Too many for me to recommend anything specific to you without having to re-surf the net for half a day. The baseline is all oils are a compromise to begin with i.e.:

• Cold start flow
• Film strength/viscosity under high temp, high shear conditions (extended full power runs)
• Environment (ZDDP harms Cat converters)
• Shear stability (how much viscosity is retained during oil life)

A 0W oil is good for sub zero start ups, the lower warm viscosity (usually W40 max) is not necessarily good under high temp high shear conditions, especially given the fact that oil degrades over time and after 5000 miles all that's left from the 40W it says on the container is 25-30W (real life example).

A new W30 or W40 might give a small power increase over a 60W, so is perfectly good for short distance racing followed by an oil change. In endurance racing or street applications it is better to compromise a little power for safety.

So what's the perfect compromise??? I for one choose to go the 10W60 full synth route as chosen by the likes of BMW M-power for example.

Here are some nice links:

ZDDP:

http://www.lnengineering.com/oil.html

Ferrarichat vs. AEHAAS...pay attention to posts by Haith: a true oil professional

http://www.ferrarichat.com/forum/sho...&highlight=oil

sml

where can we find this for a 964?

Unkle

Thanks for the information Evoderby,

Really interesting to get your thoughts, i haven't seen Haith before only info from a guy called Doug Hilary i think Doug is from the bobstheoilguy site, both seem to give informative info on the subject. As you rightly say it is a balance and your own conclusion has gone for 10w60 to remain a little thin at start up and provide cover at high working temp (simplistic version i know).

I have read a great deal on the ZDDP, and that is a whole other subject, i did post a link to in my opening posts. I think it was a GM test and its conclusions were at odds with other info i have read. Like the high pressure is good question i was getting at at the begining. (which you and others are helping to answer).

I plucked a couple of bit from Haith that seem interesting

Since many of us have the older style engines 1960 -1980s [flat tappet-ZDDP-lower tolerances etc] I suspect we may have more issues than the 1990s-present style engines. Do you subscribe to the following notions:

A. Older flat tappet engines require 1200 ppm ZDDP as a last line of defense when the
oil shear limit is breached.

B. Approx. 70%-80% of engine wear/tear occurs during start up due to viscosity[10W]
being to high to properly lubricate the engine, therefore a 0W should be used.

C. A 10W-50 oil that was required back in the 1970s is equivalent to a 0W-40 synthetic oil.

D. Once an engine is properly warmed 185F-195F the ratio of oil pressure to engine rpms
should follow something approximating this sequence 30psi/2000rpm, 40psi/3000rpm,
50psi/4000rpm

As a side note, I have used a 0W-40 full synthetic and 15W-50 full synthetic, and have not seen a big difference in terms of oil pressure. My 1980 Merak calls for 10W-50 dino oil as per 1980 factory requirements. I have not been able to find that weight oil here in the States. Not to be flippant, but would viscosities average out if I mixed the two above mentioned synthetic oils in a 50/50 blend?

Your thoughts please.



I work for a major international oil company so on that basis I won't recommend brands as I'm obviously likely to be biased! In my F355 I use a fully synthetic 10W 60, with my sole requirment being to use the best formulation / viscosity for durability (in other words I'm not concerened about losing a little power or fuel economy).

A) The majority of modern day Ferraris are still using flat tappet followers as opposed to a roller design (roller followers unlikely to be able to go to as high speeds) so in that respect the anti-wear requirements are probably fairly similar to the older cars. The main change has been to Ferrari designing hydraulically lash adjusted followers capable of operating at the high engine speeds instead of having to use shims to provide the correct clearances.

B) Wear under cold startup conditions should not be underestimated. I only use my F355 during the warm spring and summer months, hence the reason I'm willing to use a 10W. The pumpability of a 10W under relatively warm ambient cold starts should be fairly reasonable. However, if I was using the car during the winter I would be using a 0W 40 as you suggest. In fact I use a full synthetic 0W 40 in my everyday car.

C) I'm not too sure what you mean by this George but I suspect you are asking whether a modern 0W 40 fully synthetic oil is a sensible substitute for a 10W 50 that was originally specified for the car. I would say as long as you aren't using the car too hard or under very hot conditions it should be fine.

D) I don't really have any particular input on this I'm afraid. I know there are general guidelines that people talk about but so much of it depends on the engine design, the oil pump specification, relief valve etc.

Under normal operating conditions I'm not too surprised that you haven't seen a large difference between the two viscosity grades you have tried, however I'd expect a fairly big difference under warmup (cold start) conditions. I wouldn't recommend mixing two different oil formulations in order to try and end up at a viscosity mid-way between. There are many complicated chemical interactions within a lubricant that could potentially become antagonistic when different (unknown) chemistries are mixed. The risk of a major problem is probably slim, but I still wouldn't advise it.



Some info from Doug

The Porsche TISBs are applicable back to MY84 and viable for 993 engines

The factory uses 15w-40 mineral lubricants in its own early aircooled engines and 20w-50 mineral lubricants (warmed up to 80C before revs or load is applied) in its older race engines

For a 993 the 5w cold start rating is important IMO and a SAE50 mineral lubricant without it is probably undesirable. The Brand is largely irrelevant!

A 5w-40 viscosity "mixed fleet" synthetic HDEO is a viable non Approved lubricant for a 993

tilley - M1 is a PAO product - the exceptions are M1 0w-40 and M1 TDT 5w-40 (aka Delvac 1 5w-40) which are both Group 4/5

A Driver's Handbook is a "Sales" document and is a general statement in time. It shows what can be used for a vehicle marketed Internationally (usually) and where perhaps only a limited number of viscosities are available

TISBs are the products of experience and are issued by the manufacturer's Service Engineers. With German vehicles at least it has been this way for over fifty years that I know of and have been directly involved with

For instance since 1990 no SAE30 lubricants of any type have been Approved by Porsche. This is due to a lack of a suitable HTHS viscosity during extended test ACEA protocols. Such a lubricant will be in your Handbook however and I am sure no thinking (Porsche) person would use such a lubricant unless it was the only one available and needed for some dire reason

As an example a recent survey of lubricants for Porsche 928 V8 engines showed some disparity between Handbooks, Service Information Books and Technical Information Service Bulletins (TISBs). It showed that from 1984 until the end of production in 1995 Porsche moved via TISBs from Listing any 15w-50 or 20w-50 lubricants to 5w-40 and 0w-40 (and Mobil 1 5w-50, the only Approved SAE50 lubricant) meeting at least ACEA A3/B3 specifications
There is a good reason for this as these 32V engines have hydraulic lifter/adjusters and a need for at least a 3.5cP HTHS vis. They have a relief valve setting at around 8-9bar too!
As well it is known that an independent Porsche Service point in Sydney Australia used an unsuitable 25w-50 mineral ACEA A2 (and TBN 8) lubricant in these engines at this time. This is quite common practice when outside the Manufacturer's loop - I have seen this many times before and ultimately to the vehicle owner's detriment

It is well know that for the same reasons (valve actuating technology) the M96 engines are almost universally on a 0w-40 lubricant and with now many years of user and Warranty experience. No mineral lubricants have been Approved by Porsche since MY1999 yet my MY2001 Handbook lists a mineral 20w-50 lubricant option!

Porsche TISBs for non Cayenne V6 (VW) engines show around 30% are 0w-40 viscosity, 70% are 5w-40 viscosity with M1 5w-50 being the sole SAE50 lubricant Listed. And believe it or not M1 5w-50 is quite a different "animal" to M1 15w-50 from a "flow" perspective

Why doesn't Porsche advise Owners? - well they do via their Dealerships. In their Handbooks of recent years they also say "use only a Porsche Approved lubricant" or as such


As you mention you can read and find lots of info, some helpful some confusing




Do you have any other data on pressure than, 5000rpm 5bar approx which is in the workshop manual and the "light may come on occasionally" at idle?

Thanks again

rarebear

I always was told that 10 psi at idle (800 rpm and hot engine) is about the lowest permissable pressure... Porsche does not give any clue in the owners manual and the 'experts' all tell different stories... what am I to believe ?

Olcha911

That is correct. I have rebuilt a couple of 964 engines and owned 964s for about 16 years. If you are using your stock gauge (I have also hooked up a mechanical gauge) a hot engine (middle of the oil temp gauge) should idle right at, or a hair below the 1 bar white mark.

A healthy engine will gain about 1 bar of pressure per 100 RPM,and you should see the oil pressure gauge "pinned" at the top about 5k-5.5k RPM. You should not have to go past 6k RPM to pin the gauge.

Also, the oil pressure warning light (idiot) light will come on if pressure at idle is below .5 bar. If you don't see the light you are still okay as long as the oil pressure builds as described above.

-Keith

evoderby

In the workshop manual, I think* Porsche states 4Bar @ 5500RPM @ 80degrees Celsius. This equates to 0.73Bar pressure per 1000RPM

*I don't have current access to my manuals, I could find confirmation on the net that this is what Porsche states for the 3.2 Carrera

The low oil pressure warning switch operates between 0.5-0.6 Bar which at idle (850RPM) equates to about 0.65 Bar per 1000 RPM



The rule of thumb 0.7Bar / 1000 RPM posted earlier fits rather nicely between the two, so Porsche seems to agree....

evoderby

You are more than welcome! Indeed lots of the info to be found on the net can be confusing.

In my personal (non scientific) approach I start from one firm base assumption:

Porsche knew what they were doing when designing the 964 engine in terms of oil pump volume capacity, oil passage way drag and bearing clearances.

Leading to the following conclusion:

Therefore they also have a good understanding of the pressure readings required (given the bandwith of viscosities allowed) to indicate a 'healthy' engine, a not so healthy engine as well as acute danger.

My first assumption could be incorrect, making my conclusion invalid. I for one think it's a rather safe assumption however, which helps me sift through the many articles and opinions posted on the net....in the end it comes down to this: good pressure combined with good quality oil = no more sleepless nights!

As far as more data on 964 Pressure is concerned I really don't have much more than what Porsche states - see previous post - which almost exactly equates to 0.7Bar / 1000Rpm.

One question that I still have is if 75% of engine wear really occurs during startup, for which 0W is better than 20W, why doesn't every car simply comes fitted with a Canton/Moroso accusump type pre-oiler??? I sense a conspiracy just waiting to be revealed!!!! ;-)

Unkle

I also subscribe to the "they know what they were doing" theory, and with the racing heritage of Porsche going back to the Panamerica days and beyond, i think they have built and destroy a fair amount of engines and probably understand what is and isn't needed for all climates and conditions when it comes to oil. They aren't perfect or infallible but with TISB will share the info with mechanics/technicians.

On the start up issue. I again always thought start up meant "starting up", but from what i read it actually means "till operating temp", which is very different to the first 5 seconds after the key is turned (as i thought before). If that is correct that would be a long time where increased wear can occur if people use a very thick oil. If its 5 seconds perhaps not but it appears from what i have read we are talking about a fairly long period of time. how that relates to your conspiracy? Who knows

Henry964

The startup wear issue is related to the - probably less than 5 seconds - that takes the oil to get everywhere, once the oil arrives the wear of metallic parts is much less, that why I am a big believer in using oil that has Mos2 or other similar substance (Magnatec by Castrol) as an additive

evoderby

Hmmm, so what we need is both a pre-oiler and a sump heater as used in very cold climates;-)

I've done some quick reading on the cold start wear issue. Some sources indeed suggest that while 80% of engine wear occurs during start up, only a small amount (15%) of this is related to a lack of oil flow during the first few moments (seconds) of start up.

The major part of the wear is accounted to the engine not operating under ideal operating temps (i.e. not warmed up yet which indeed can take anywhere from 5 up to 20 minutes). This really has very little to do with oil viscosity.

The causes mentioned are:

• Bore wash due to overly rich fuelling at cold start (choke effect)
• Piston rock in bores while cold (pistons are oval in cold state and have 5x more clearance compared to operating temp)
• Water condensing in cold cylinders mixing with combustion products (especially sulfur) and the resulting acid reacting with bores/rings and also mixing with oil
• Some oil additives aimed at protecting the engine also have to reach operating temps well above 50C celsius to start functioning.

http://www.bobistheoilguy.com/forums...2145915&page=3


All pretty cool stuff, and definately worth it doing some more reading on the subject at a later stage.

Could it be that all the low viscosity oils (usually also low ZDDP) marketed to reduce start up wear only do so by the narrowest of margins compared to a thicker oil? Is their main purpose reducing fuel consumption and emissions to help manufacturers pass legislation? Is increased engine wear under arduous conditions calculated into the equation and simply accepted?

Next time on Batman.... ;-)

Unkle

Thanks Henry/Evoderby


Both slightly conflicting about start up wear (isn't that always the way) but either way i think an acceptance of cold wear takes place until oil is at operating temp. I can understand the lower hot temp of oil, say to a 30 grade and that this would be for fuel saving etc and not cold start related. But for most manufacturers to drop the cold starting temp, would imply perhaps a revision of older concepts on the oil when cold? They seem to follow an ever increasing theme, except for the users of the 964. Not that its a concern but it doesn't seem to follow possible understanding by leading car manufacturers or oil companies. (why i am trying to understand it more)

From that link you posted

In order for oil to fully protect, the engine and oil have to be at optimal operating temps, which can take up to 20 minutes or longer to reach. So the startup wear is occurring until the engine oil reaches optimal temps, usually 20+ minutes

The largest contributor to wear when cold is the fact that the operating clearances are not to specification. Different metals expand at different rates. Until the engine is fully heat stabilized the clearances are off. The most striking example is pistons being oval. They are machined out of round so that as the various thicknesses of metal heat up the piston achieves a round shape.

It appears to indicate from that article and many i have read, that low start up viscosity can't ever be a bad thing "if" you maintain the hot working temp to manufacturer specs. so for example a 0w40 is better than a 5w40 and better than a 10w40, 15w40 etc. Or if you start higher, say you use a 10w40 then a 5w40 would be better for example... (all things being equal)


Perhaps in a hot working environment or track work necessitates higher hot working temp a 50 grade is better or more, but i read that it should be used with the lowest type of cold temp possible, for example you are using 10w60, Which would seem logical, yet this again is at odds with the 20w that many use. This was the reason for starting the thread.

Anyway its a subject that runs and runs, but at least it have remained polite and educational

Mc.Queen 964

Guys, I've got a question.. 5w50 is EXACTLY as thick as 20w50 at hot? I know that second number is density of oil when hot, but it's exactly the same? I'm changing valve relief and spring relief, because my oil pressure at idle is 0,6-0,7 at 850-900 when REALLY HOT, so I want a thicker oil at hot.

May a 5w50 fix it if valve relief changes doesn't work? or I will have to change for example to 10w60?

warmfuzzies

This is an interesting area, the weight of the oil does not qualify it's thickness, only it's properties under certain conditions. and W stands for Winter. the upper weight normally measured at 210 F
So you can have a very thin completely synthetic that will behave as a thicker dyno oil, but look and feel completely different, hence my earlier comments regading misting off.

Look for oil flashpoints if you want an indication of how these vary.

regards

kevin

Quadcammer

bloody hell, I would not, under any circumstances, run a 0w-40 in an air cooled 911.