here are some comments that may assist with this thread - they only apply to engines that are not raced;

1 - Bill & Matt-
<<15W50 M1 too thin? I didn't go back and read Doug's stuff, but I think he argued that 15W50 is too thick and that you get high pressure at the expense of flow. My problem is that 5W40 is OK except when I idle to a stop at the end of an open road race. The engine is very hot and the pressure is too low. I would like to idle the engine to cool it off, but I have to kill it due to low pressure. Let it cool down and all is OK. Perhaps my bearing clearances are a little high at 160K miles, in which case I would think the high viscosity is OK if not beneficial. Bill>> <<Doug said M1 15W50 is not specifically approved by Porsche. 15W50 is an approved viscosity according to the owner's manual scan in post #43 in that thread. Matt>>

As you indicated, the "CarCraft" article is "inaccurate" in that it is at least 6 years and maybe even 10 years old. It states "Mobil 1's new Tri-synthetic..." (It has had three formulation changes since) and the API's "SJ" quality rating as current - it was, in 1997 and is now SM!
Some information contained in the article is still "conventional wisdom" however and some quality synthetic oils do protect well into the 400F range - and do it very well indeed!
In some racing applications monograde oils still rule - ask Castrol who still sell lots of Castrol R30 and R40 ester based oils (with the BEST smell) for racers

2 - Oils have changed dramatically over the last 20 years and the API have had three quality rating changes in the last decade alone. ACEA have had four quality rating changes since 1996. So articles that are older than the last quality upgrade (s) will have some inaccuracies when viewed from today's perspective

3 - Matt - oils fall in to six Groups. The synthetics fall into Groups 3 to 5. Group 6 is a new type of synthetic composition. Old semi-synthetic oils that fell into the Group 3 "hydro-cracked" category have been updated to rival Group 4 or 5 synthetics - they are still Group 3 "synthetics". Many now outperform some boutique synthetics at half the price!
John, good to hear from you. The latest range of Approved Castrol engine oil products are performing very well in service in Australia - especially the fully synthetic 0w-40. As mentioned once before if I were to race a 928 engine I would use Castrol's R synthetic 10w-60, an oil that I assisted in developing from the late 1970s into the early 1980s

John as you indicated, many advanced additives and lubrication "structures" are already in use or will be in the next year or two. Some of these may be far superior to Moly etc. and some indications are that mineral or synthetic base oils and ester combinations using these new additive packages are top performers. Whilst technically Group 3 oils they outperform some "old" and very expensive Group 5 synthetics
Ferrari appear to use a Group 3 base oil from Shell suitably "tuned" of course

4 - RDS928S -
<<Porsche factory approved oil for all models is Mobil 1 synthetic 0-40w.
My Porsche owners manual from 1986 approves of multi-viscosity oils including synthetics in the range of 10-30 & 10-40.
Porsche refers to these oil weights as "fuel efficient". RDS>>

Porsche factory filled 928 engines with two different viscosity synthetic oils - initially a 10w-30 and after 12 months production they went to a 5w-40.
Both were Shell products which Porsche used up until the mid 1990s or thereabouts

Porsche testing regime's standards only Approve synthetic oils and the factory still fills with either a 0w-40 or a 5w-40. Using either of these simply depends on the LOWEST consistent ambient that the engine will be used in.
An about even mix of both 0w-40 and 5w-40 oils are on Porsche's Approval List

5 - Tim-
<<Needless to say...Doug Hillary is very qualified and his opinions are very welcome. I just wish he could do something to cure this 5w-40 Truck/SUV formula shortage. Tim>>

Mobil's 1 5w-40 T&SUV has been repackaged and is now called Mobil 1 Turbo Diesel 5w-40 in the US I believe - and it can be used as a replacement.
I use Delvac 1 5w-40 HDEO (Heavy Duty Engine Oil) which is the original and Commercial version of these oils has a high ester content and has been around for about 15 years.
It should be available from Mobil Truck Stops or a Mobil Distributor
By any standard today a ??W-40 oil is quite viscous - many new engine run very well on their prescribed diet of a mineral 0w-20 and so did cars made in the 1940s!!!
Euro engine manufacturers have long settled on the ACEA A3/A4 criteria which by and large calls up a 0w-40 or 5w-40 lubricant - mineral or synthetic. This is changing and some Euro engines will go down to 0w-20 in the near future in order to improve fuel efficiency - these oils have a HTHS viscosity of 2.9 cSt or thereabouts and are unsuitable for a Porsche. Never use M1 10w-30 in a 928 for this very reason


6 - Porsche's Approval system requires the lubricant to meet their own specific anti-foaming and volatility requirements etc. along with the ACEA's A3/B3 quality test ratings
No 10w-30 oils meet these requirements and many oils without Porsche Approval may not perform too well in a 928

IMHO and in particular, Porsche's minimum High Temperature High Shear (HTHS) viscosity of 3.6cSt at 150C is quite critical to a 928 engine's health. Personally I prefer this viscosity to be around 4cSt for a 928 and that is why I use Delvac 1 5w-40!

7 - Some oils like certain Amsoil products tend to thicken with normal use - Mobil 1 0w-40 tends to thin and then thicken again but holds its viscosity over extended drains. Amsoil products are NOT Approved or Listed by Porsche - one however (a Euro spec 5w-40) is Approved by Mercedes Benz and performs well in their test regime
Amsoil's (and some other boutique oil blenders) range of oils includes (ed) many that were uncertified by the API. This was a marketing decision by them but many believe that the level of some additives would have precluded them from certification. Hence these oils say that the "Meet" or "Exceed" the API's quality standard but have not been officially Certified

8 - Oils that thicken excessively with use do tend to introduce internal deposit problems and they need to be changed more often. This is more evident with the conventional (mineral) and cheaper 20w-50 lubricants and etc. They tend to oxidize quickly and have poor cold flow characteristics

It is worth remembering that the original 20w-50 oil was prepared solely for the BMC Mini's release in 1959. It was produced to compensate for excessive oil shearing due to the combined engine/transmission in these vehicles (sharing the one lubricant).
The first 20w-50 was produced by Duckhams and quickly followed by Castrol

Even with Mobil 1 15w-50 (an oil with excellent cold flow abilities) Marc from DEVEK produced a dyno engine report giving an oil temp/viscosity/revs result which showed that the engine's lubrication system and the filtration media may still be in by-pass after 10 minutes running as I recall

9- Most wear is presumed (and confirmed) to occur in the cold start period until the oil's Anti-wear (AW) additives are activated. This is usually above about 60C oil temperature. Oil temperature in a 928 runs about 10C behind coolant temperature for up to 30 minutes after a cold start
A 5w-?? synthetic oil will circulate much faster than a 20w-?? mineral oil and will tend to heat up a little quicker. This is important in a 928 with a very high relief valve setting and hydraulic valve train actuation

10 - Chris -
<<My recollection is that Doug's recommendation for 5w40 is for normal street driving, not for racing, and that he sees no problem with 15w50 for such high stress application. I don't think he had an argument that it was bad for the car, just that on the street, 5w40 had some advantages for startup protection and fuel economy, as well as for those in cold weather, while still being perfectly fine in higher temperature locales like Doug's. Chris>>

You got it right! Mobil 1's 15w-50 is NOT approved by Porsche only the 5w-50 version is. It is the ONLY SAE50 oil Porsche Approves. M1 15w-50 should only be used in a consistent ambient down to -15C (0F). These two oils are quite outstanding products and work well in a 928, and in cold weather too use them with confidence. For most a 5w-40 synthetic will work better!

11 - No oil has been shown to significantly reduce wear over another meeting similar specifications (such as ACEA A3/B3-04 or API's SL/CF). This applies to brands and composition (mineral/synthetic). Don't believe the advertising hype - that's what it is, hype!
Benefits are certainly there when using a synthetic as Porsche recommends and as they have done since 1992 - these can be viewed as extras for the premium in price!

12 - It is wise not to confuse flow and pressure. Pressure is "only" a measure of resistance!
Porsche only provides data on minimum hot oil pressure at 4-5000rpm - you need 5bar!.
Most 928s will show 4bar at 2000rpm and this is great!

As long as the hot idle OP is around 2bar and above at idle all is well. Oil flow will be the same at idle whether you have 3bar or 2bar etc. but it is worth replacing the oil cooler's thermostat if a consistently low OP occurs at hot idle

13 - Used Oil Analysis (UOA) is a great way to determine if an oil is performing well and its condition at one point in time. Trending the results can show if an engine's wear metal rates are consistent and "normal". In the case of a 928 if can be used as another tool to pre-empt the possibility of thrust bearing failure

14 - Sam - we have never met. I live in Airlie Beach and rarely get to Sydney - you are welcome here anytime
Sadly mechanics do not get trained on lubricants and most merely "go with the flow"
My two youngest sons are diesel mechanics in Brisbane - one (26yo) is with Caterpillar and the other (24yo) is with MAN-VW-Western Star-Mercedes Benz. They are appalled at how little their TAFE Tutors really knew - it's a worry!

Well, sorry for the long post but I hope it assists in understanding more about our wonderful cars

Doug Hillary
Matt - the 0w-40 is a great oil, possibly one of the best engine lubricants made to date by anyone. In your case I would use up the M1 15w-50 with confidence - and look for stocks of the M1 Turbo Diesel 5w-40 or Delvac 1 5w-40 for use next time

Mark I was tempted to answer your post but decided one cannot match a marketing beat up!

As for the 4 ball test well......! Big balls or not?

As John has indicated the Amsoil promoted "4 ball" test is really a test for grease!
The 4 ball test is totally irrelevant to engine oils and even many Amsoil Dealers are so embarrassed by it they have sought to have it dropped from Amsoil's marketing plan, It is that irrelevant!

No other engine oil blender or producer uses this test for their products

No engine manufacturer uses the 4 ball test either and this applies to all engine manufacturers - diesel or petrol and from any Continent you name!!

There is another thread here on the 928 Forum entitled "Oil foaming". It too is full of biassed marketing by Amsoil! Sadly the Amsoil products mentioned there do not have any diesel engine maker's Approvals! And in this test Amsoil wins again - in Amsoil's test!

The issue of oil foaming and silicon is misleading to say the least. It is very common to have small amount of silicon polymer leaching evidenced in used oil samples (UOA) after new gaskets or seals are fitted and where silicon sealants used. The highest I have seen is around 110ppm - not a lot when you know where it comes from and that it is simply not ingested via the air intake as a silicate

As to its affect well I have seen evidence of a silicon oil seal being replaced and the the UOA going from 7ppm to 96ppm within 24kkms due to leaching - there was no adverse affect and I have never seen evidence of any serious problems. This sort of thing at low ppm concentrations is very common
Always use the oil specified/recommended or Listed by the engine's manufacturer -this is especially so with high speed diesel engines

Mark the Porsche/Mobil relationship has nothing whatsoever to do with the Porsche Approvals List!
This List contains about 100 (around three are Mobil 1) or so engine oils with official Porsche Approval - Amsoil is nowhere to be seen!

It is a fallacy to think that an oil supplier does not work closely with the engine Manufacturer! Look at Shell in Formula 1 with Ferrari and well publicized too.
In that role I can confirm the extremely close engineering relationship that does exist between Mobil and Mercedes Benz and between VW-Audi and Castrol and etc. I have been there and done that!!

Some Amsoil products are no doubt very good and the Euro formulated 5w-40 which has Mercedes Benz Approval is one. I just wish that their marking would be less misleading and that they would obtain Manufacturer Approvals and certification on the established level playing fields of both API and ACEA

John - the idea of using a suitable monograde when racing is excellent - is it Castrol's R30 or R40?

In the end use what you believe is best for you - remember though that NO oil is significantly better than another if both meet the same specification!


Please post on the oil foaming thread. The info I posted is from Amsoil but I posted it because of the silicon info. Aren't desiccants also added to oils as anti-foaming agents? I'm currently using Mobil truck/SUV 5W-40 and noticed my oil pressure runs about 4 bar at 2000rpm and 1.5- 2 bar at idle.
Doug, thank you very much for sharing your in-depth knowledge on oils for our cars. I've been running Mobil 1 15W-50 for ten years now b/c Leonard Laub and Ed Ruiz used to recommend it on the old Porsche Fans list, and I have no real independent knowledge. I change my oil every 12 mos. (usually 3-4 K mi) and am very relieved that you confirm that the Mobil 1 15-50 is a good product for our cars that presumably won't do any harm. I tried to find the T & SUV 5W-40 for my most recent change, but like many others have discovered, I couldn't find any. Wal-Mart had 5 QT jugs of the Mobil 1 15W-50 so I stuck with it. I'm surprised DEVEK found the motor in bypass for 10 mins. The stuff seems to pour pretty freely even at room temp (which here in Alabama is usually pretty warm). I'll keep my eyes open for some Mobil 1 5W-40 for next year's change, but won't sweat about the 15W-50 I have in the car. Thanks again for your great info.

'89 S4 Auto
As mentioned once before if I were to race a 928 engine I would use Castrol's R synthetic 10w-60, an oil that I assisted in developing from the late 1970s into the early 1980s.

Ah, so this is what BMW has been using a lot. What do you think about using this in my 89 daily driver, supercharged, open road race car? This car never sees weather below freezing and spends most of it time in warm to hot weather. I want to get something with start up less viscosity than 15 in 15-50 M1 I use now.
Hi Bill,
yes, this Castrol lubricant is a truly great product

Its startup viscosity may be a little higher than M1!

While its Pour point is similar to M1, see below:
Pour point:
M1 15w-50 = -45C
"R" 10w-60 = -42C

it is much more viscous, as follows;
at 40C:
M1 15w-50 = 125cSt
"R" 10w-60 = 170cSt
at 100C:
M1 15w-50 = 17.5cSt
"R" 10w-60 = 24cSt

Its HTHS viscosity (@150C) is also higher;
M1 15w-50 = 5.11cSt
"R" 10w-60 = 5.4cSt

BMW do endorse this product for certain engines - the "M" series for instance and ALPINA vehicles

It started off as a castor based oil with a great smell to what it is today - a truly great lubricant in the right application

Because of its formulation it is expensive when compared to some other synthetics - you get in this instance what you pay for!



This is discussed often on the web forum http://forums.rennlist.com/  this is Doug Hillary's last post on the CGT board, he also has a lot of oil posts on the 928 board.
High Temperature High Shear (HTHS) viscosity has received a lot of attention over the last several years from engine designers and oil companies. As fuel efficiencies dominate future designs (internationally) engines become more complex which in turn places a greater emphasis on secondary systems such as lubrication

As well and as a result a better understanding of the principles of both temporary and permanent shear is being addressed. This is being aided by the use of more advanced testing technologies such as real time wear measurement using radioactive tracers and etc

The ACEA has these comments concerning HTHS viscosity:
(A1/B1 quality rating)"Oils intended for use in gasoline and car/light van diesel engines specifically designed to be capable of using low friction low viscosity oils with a HTHS viscosity of 2.6 to 3.5mPas.s. These oils may be unsuitable for use in some engines. Consult owner manual or handbook if in doubt"


(A5/B5 quality rating)" Stable, stay in grade oil intended for use at extended drain intervals in high performance gasoline and car/light van diesel engines designed to be capable of using low friction low viscosity oils with a HTHS viscosity of 2.9 to 3.5mPas. These oils may be unsuitable for use in some engines. Consult owner manual or handbook if in doubt"

The latest catalyst compatible quality ratings under ACEA ("C1,2 and 3) with the HTHS viscosity above 2.9mPas are another matter as well. These are known as the low SAPS oils ("SAPS" is Sulfated Ash, Phosphorus and Sulfur) and are mandatory now in some engine families

NOTE: Anybody using an HDEO in a petrol engine ((911/912 etc) should ensure that it is diesel/petrol rated (say CI-4/SL). Some diesel only rated HDEOs have very high sulfated ash levels. These deposits can cause accelerated wear in some engines

So you can see from this that your comment regarding "design" is most relevant.

Euro manufacturers have long used the higher HTHS viscosity (>3.5mPas) rated
A3/B3 and A3/B4 quality ratings for their engines. There are many and varied reasons for this that would take too much time to suitably cover here. But of course they do include the wiping loads on camshafts, lining, ring and combustion chamber design and the hydraulic function of the lubricant to name but a few

Any relationship of HTHS viscosity to HP/Litre output would be mainly circumstantial I expect and I know of no specific research done on that issue Usually a turbocharged engine is more demanding than a NA or Supercharged engine on certain aspects of its lubricant's performance. Again design and application play a huge role!
M1 0w-40 which has a HTHS viscosity of 3.6cSt is used as factory fill in AMG and Porsche engines - some NA, some supercharged and some turbocharged. It is also suitable and recommended for use in many high performance diesel engines

I believe that the Euro and other engine manufacturer's research has shown that the HTHS viscosity of 3.5cSt is suitable in a wide range of engine families. (The minimum HTHS viscosity for 15w-40 HDEOs is 3.7cSt).
Above about 4cSt the higher HTHS viscosity begins to affect the rate of frictional losses

Below a HTHS viscosity of about 3cSt, significant wear may occur when such lubricants are used in unsuitable applications. Where Ford & Honda etc seek an HTHS viscosity of 2.6cSt they (apparently) have not had any exceptional engine or component wear issues

Remember that the oil film's strength is not dependent on oil pressure. In the crankshaft's (and other Journal type) bearings area for instance the "oil dam" affect occurs in front of the journal and pressures here reach way beyond that generated by the lubrication system's oil pump. This is why oil flow is so important - the more linear the oil's flow characteristics (with full synthetics) the better the flow rate and the oil's cooling potential!

At present a lot of design and development is being done on such things as;
a) lowering the HTHS viscosity of lubricants for high output high speed diesel engines,
b) the use of advanced actuation devices (valves and etc),
c) measuring oil conservation/extended drain requirements (oil formulations, filtration on board oil conditioning devices, on board oil condition monitoring packages) and etc
d) advanced metallurgy and engine components durability testing

Low viscosity SAE 10, 20 and 30 monograde lubricants were very popular in the 1930s and well into the 1970s. Their return as short viscosity span (say
0w-20) multigrades is now primarily driven to reduce internal friction thereby improving fuel efficiency.

As for your comments regarding Mobil and the Honda Civic I can only relate this information.

To my knowledge Mobil only make a mineral 5w-20 oil and its structure is unknown to me as these are not sold here in Australia

M1 0w-20 has a HTHS viscosity of 2.61, 40C viscosity of 43 and @ 100C, 8.4.
M1 0w-30 has a HTHS viscosity of 2.99, 40C viscosity of 53 and @ 100C, 10.3
M1 5w-30 has a HTHS viscosity of 3.08, 40C viscosity of 53 and @ 100C, 10.8.

M1 10w-30 has a HTHS viscosity of 3.17, 40C viscosity of 62 and @ 100C,10

Note the relatively big variance at 40C between the 0w20 and the 10w-30 viscosities

Group 3 (semi-synthetics) and Group 4 synthetics will typically have a more robust base structure than a mineral equivalent but the HTHS viscosity may only be slightly higher enabling the fuel efficiency CAFÉ ratings. Many Group 3 lubricants are being formulated as low SAPS cost effective products and performing very well indeed

The issue of lubricants is very complex today. I have always advocated following the engine maker's recommendations. Specialists and Tribology "experts" can of course afford to be perhaps a little more adventurous in the lubricant selection

NOTE: "ACEA" is the abbreviation used for the Euro vehicle and engine makers consultative body

As for inaccuracies on websites, there are many. The Oil Industry is certainly not immune to errors at that level. The Driver's manual is always a great reference point

I hope this is of some interest