martin D

Nick
I don't think it's readily available in the U.K., I did find some here though, I know nothing about the supplier or even where they are ?
http://www.oil-store.co.uk/en-gb/dept_7.html

£86.20 for 20 litres

at some stage in the near future I will be looking at buying in bulk, so may be cheaper.

Warren928

Interesting data. I just found out a friend of mine became an Amsoil Dealer. Amsoil has a complete line of synthetics that I just started using. They have a 25,000 mile oil (about $6.50, only the filter needs to be changed after 12,500. The wear results and data are impressive from amsoil, not suprising since they have pioneered synthetic oil and have been doing it a decade longer than mobil.

One guy ran synthetic in his diesel truck, changed it over to amsoil. He Only changed the filter in regular "extended intervals" and had the Amsoil oil tested instead of changed to see if it was holding up okay. the truck ran 400,000 miles on the same oil (yes, never changed it!) and when they took the engine apart, the truck mechanic inspected all the parts and they were all reusable. They show almost no wear at all.
My friend is going to get me the video showing the whole thing. Pretty impressive oil. They say dinosaur oil is good for around 600psi, where as Amsoil is good for lubricating in up to 2400 psi applications.

Its amazing what these new oils are capable of.

Kaz

I'm not sure if the 928 I have now has ever used synthetic oil, is it harmless to switch over now with nearly 200,000 miles on the odometer?

Chazz

Doug, do you have any statistics on the relative performance of good quality mineral vs. synthetic oil for normal usage in the 928? In your opinion, is there any truth to the notion that sythetics are more likely to leak?

Doug Hillary

Hi,
Warren928 - don't believe too much of the Amsoil advertising "music" - despite the hype there is NO magic lubricant! Amsoil is but one of a number of excellent "boutique" oils. Most buy their base stocks from one of three large suppliers - ExxonMobil supply most to Amsoil!!
Amsoil were not in the synthetic oils game a decade before Mobil and both released synthetics to the retail market around about the same time - give or take a few months. Synthetic lubricants were patented in America in the late 1800s and today's synthetics were pioneered in Germany during the early 1930s
Reports show that Amsoil will not last the distances you describe without seriously thickenong out of viscosity and Porsches change intervals for the 928 should IMHO not be exceeded unless using Used Oil Analysis as the basis (with any oil)

Bill, John - yes Castrol make some very strange marketing moves. One of my best friends and an ex employee - a longtime Castrol Engineer - cannot even keep up with the play today. BP the owner of Castrol also now sell their re-badged products of course. IMHO some of Castrol's gear oils and their synthetic ATF (Transmax Z) are simply the best. Some of their engine lubricants are leaders in their respective field - Castrol "R" 10w-60 which I did some field development work with in the early 1980s is but one

Kaz - a modern correct viscosity synthetic engine oil should not cause any additional seepage or cause leaks to develop. Some (ester based) may in fact cause enough seal swell to inhibit them a little.
As to the advantages well a lot depends on what lubricant is currently being used and what came before it. The highest milage car I have converted was at 150kmiles and one of my trucks was done at about 500kmiles - no leaks developed. The many I have done between these figures were also trouble free until eventually sold
You are more likely to develop leaks/seepage when changing from mineral gear oils, ATF and in a 928's power steering
Kaz please contact me via a Private Message if you wish

Chazz - Your question of the benefits - mineral v synthetic - would really require a detailed answer and this has been debated here before.

In short and in general then the benefits are;
-at the top and bottom of the temperature range of car use (may be quite significant),
-better more linear flow at all temperatures (cooler component running),
-better engine cleanliness (with some real benefits)
-possibly longer oil life (debateable)
and etc.etc.

Todays modern semi-synthetic Group 3 oils that have Porsche (or DB) Approval (or are ACEA A3/B3-04 accredited) are truely excellent products and much cheaper than the likes of Amsoil, Redline, Royal Purple and etc - and IMHO are probably just as good or better. At a similar specification comparison of course!!

It has NEVER been conclusively proven at any level that when using two similarly specced oils - one mineral and the other semi or fully synthetic - either will make will make an engine last significantly longer when it is used identically!

I (in conjunction with Detroit Diesel and Mobil) had DD tear down a 500hp engine of mine about a year ago that had completed 1m kms (620k miles) on Delvac 1 5w-40 for a wear analysis. All parts including the valve gear and rings passed as OK for reassembly (most unusual) and the engine was extremely clean which is also unusual for a heavy diesel. I still have this truck now with an extra 60k miles on it and oil consumption throughout its life has averaged 1 litre per 6000kms

Some other modern correct specification oils would probably have done much the same job!

The real oils answer is to know what specification lubricant is required by the engine's Manufacturer and to use it following the Manufacturer's service intervals. Any variance in drain interval should be monitored via Used oil Analysis

Regards

BC

I was trying to find the x.x number you refer to in t he high sheer test for all of the heavier oils, as I am very near Randy in The San Diego area. I have discussed this with you before, and have ALMOST simply decided to use the 10-40 or 15/50 delvac that is at walmart if thats the same stuff you have mentioned. I just am concerned about the 5/40 in the heavy hot traffic that can develop here in SoCal. With occasional track use and a low temp starting limit of only about 45 degrees (only a few days a year - the rest would be 60degrees - I was thinking it would be okay to use the heavier oil.

BUt you just mentioned that the wear rates in the most recent drain test on your 928 were lower then with the heavier oils - very interesting.

Doug Hillary

Hi Brendan,
there are a large number of Delvac Commercial lubricants and some are simply NOT suitable for use in the 928 or other engines

These Delvac products ARE suitable for a 928;
Delvac 1 5w-40 fully synthetic (which I use) and,
Delvac MX 15w-40, an excellent HDEO and non synthetic

Suitable Delvac oils will have "mixed fleet" and the API's quality ratings like these "CH-4/SJ" or "CI-4/SL" on the container's label

You may lose a little (0.5-1bar) hot idle oil pressure (OP) with a 5w-40 but the flow remains constant but Delvac 1 5w-40 (HTHS 4.1cSt) will be OK in your application.
It handles sustained high temperatures better than other oils of any Brand
Hot OP at 4000rpm should still be at 5bar however. Mine is 2bar+ at hot idle and 4bar at 1600rpm and then 5bar+ beyond 2100rpm.

M1 15w-50 SuperSyn is a great product too I believe and it has a HTHS of 5.11cSt. It is 17% more viscous at 100C than Delvac 1 5w-40

Regards

Chazz

Doug, my question was actually about statistics, not benefits. In particular, I wonder if you have data on the relative metals concentrations, synthetic vs. mineral from 928 engines. This might shed some light on the issue of rod bearing wear, a weak link in our cars' engines.

Doug Hillary

Hi Chazz,
sorry about the mis-interpretation of your question

At best UOAs can anticipate serious component wear if "trended" over time and if we know the metallurgy involved. They will not predict a sudden component failure unless perhaps a UOA was done immediately prior to/during the failure and interpreted correctly by the Lab/owner. They will accurately show an oil's condition at any time

The UOAs on millions of engines do NOT conclusively point to better wear rates when using either a synthetic or mineral lubricant. Many UOAs show identical wear rates in one engine family throughout the engine's life and I have that data on my own diesel engines accumulated for well over a decade confirming that point.
They do seem to indicate that specific engine families are more suited to a certain viscosity and/or perhaps to a formulation/brand of lubricant. VW-Audi and DB are into researching this area in a big way at this time

In my own case we DO know what the engine/oil Manufacturers wear rate/condition limits are and we use these (and our own fleet specific data) to look for oil degradation (via coolant, contamination etc) and wear metal "spikes" or companion metal upward upward trends in an endeavour to predict "incidents"
We have NOT predicted rather sudden failures like turbo bearings in my trucks or in the other large fleets I work with - and proably never will. We have used UOAs to isolate coolant leaks and overfuelling and etc. We have used our Data to accurately predict siezed cam rollers (silicon nitride) and other known engine family problem component irregularities. This saves downtime including wrong diagnosis and etc.

I think we could now predict excessive 928 thrust bearing wear (perhaps on S4 Autos & via the drive line) as long as UOAs are done say at six months or 3k miles intervals. We would need a lot more accumulated Data to support mine reported here to make the diagnosis correctly

Example:
An excessive upward collective trend (measured in parts per million) in aluminium, copper, lead and tin would "sound the warning bells"

My averages are;
Aluminium 4ppm
Copper 4ppm
Lead 6ppm
Tin 4ppm

If at the next UOA these were say A8ppm, C15ppm, L30ppm, T20ppm and all else was OK I would take another UOA quickly - within another 1k. Looking for the trend!!!
If the figures were then now C25ppm, L40ppm, T25ppm and Aluminium had "spiked" to 35ppm
I would be justified in dropping the sump as a precautionary measure. The thrust washers may well have commenced their downfall.

Knowing the mettalurgy involved is important and the above is only intended as an example

If I was into racing a 928 I would be doing a UOA routinely after each track day - it is done in F1 and in our V8Supercar series amongst many other racers. I have suggested this to Mark Kibort for nearly three years now and to Marc at Devek too!

There is a lot of data held by private and Oil Co. Labs and in the hands of people like me - sadly not much exists on Porsches. Most "concentrated" Data on engine types will also show Universal Averages against engine types which are metallurgy biased in many cases

Used Oil Anaysis (UOA) was first really promoted by Caterpillar some decades ago. It was used then to try and anticipate breakdowns and to replace components (engine, drive line, pumps), and it fitted in to their equipment maintenance regime. I like many others hoped that by using sacrifciial trace metals we may be able to accurately predict such component replacement - but to date these dreams are just that.
UOAs are done millions of times a day worldwide and by a variety of people in various Industries
Soon UOAs may be replaced by electronic and more predictable oil condition and other "predictors"!

So in short and generally, synthetic and mineral oils will show only minor variances IN WEAR METALS in similar engines/applications

Regards

Normy

Doug...what would you recommend: My car- it sits for 17 days each month [occasionally 34, though that's not likely] without running. I use Castrol 20/50, and factory filters. I was a 3000 mile change-type until your posts, now I'm leaving the dinosaur juice in the sump until the 5k mile point comes up.

I don't want to use synthetic oil. I'm worried about "kudos", or chunks of congealed lizard coming lose into suspension in the new synth oil. In college they taught that this would happen if you switched suddenly from dino to synthetic oil, and I'm pretty sure that my '85 has kept its bearings smooth via a whole bunch of stegosaurs to this point. The kudos could potentially block some of the finer oil passages, and lower oil pressure to vital areas. Also, synthetic oils introduced to a previosly-dino engine is a recipe for sudden oil leaks.

But I'm also worried about the fact that I probably have minimal oil film on my cylinder walls upon startup. When I get home [usually after being awake for over 24 hours....] I go down to the garage and start the car, allowing it to idle for 20 minutes. I don't drive it unless I do this. Then I go upstairs and become clinically dead for a few hours. Then I go out and drive the hell out of the car...after allowing it to warm up gradually.

Synthetic oil? Castrol -w- proper warm-up? What prevents initial-startup wear the most?

N!

Doug Hillary

Ni Normy,
1 - if you do not wish to use a synthetic oil then the next best thing is a "mixed fleet" Heavy Duty Engine Oil (HDEO). HDEO's are especially formulated to resist corrosion and degradation in a very harsh environment.
Castrol's RX Super 15w-40 HDEO is an excellent product. This product should easily last for a twelve month OCI as long as regular oil temps above about 80C are reached - this could be checked via a UOA at the six months point
An alternative to RX Super is the semi-synthetic Castrol Start Up (Magnatec) 10w-40 a good alround performer in 928s

2 - All modern oils (even the thinnest) do have a oil film retention test in order to pass the API and ACEA's quality certification processes. Ester based synthetics do this best

3 - Most wear is calculated to occur in getting the coolant/oil up to operating temperature and a lot of evidence exists to support this. This is why 0w-XX or 5W-XX oils are now the most commonly used - they flow quickly when cold and come off both the oil filter's differential by-pass and the lubrication system's by-pass quickly
Most oil's Anti-Wear (AW) additives commence to function once the oil is above about 50-60C

The 928 has a lot of oil and coolant to heat up. during warm up the oil follows the coolant by about 20C until reaching some equilibrium. This is one reason why the OEM 83C thermostat is so important IMHO as the 928's "core" temperature appears to lie in the 90-95C band - almost ideal. Porsche thought so too by never changing from the 83C thermostat during the 928's entire production cycle (sorry heinrich)

4 - I would never let a cold engine idle for 20 minutes and not especially a 928. Driving off conservatively after a few seconds is the trick and limiting the revs until normal idling OP is reached is very important especially if you are not using a 0w-XX or 5w-XX oil!

These figures (using an IR reader and +/-2C of course) were taken from my S4 during a test "idle warm up" when the engine was on Shell Helix Ultra 15w-50 synthetic
The results were one reason why I changed to a 5w-40 synthetic
Shown in this order = Gauge, thermostat housing, top hose, bottom hose, valve covers, vee;

@5mins = 40C, 48C, 32C, 28C, 58C, 64C
@7mins = 65C, 51C, 56C, 32C, 58C, 71C
@10mins = 75C, 74C, 57C, 38C, 71C, 74C (at this point the oil was at about 55C)
@15mins = 82C, 72C, 60C, 41C, 71C, 74C (the fans came on for 5sec at this point and the oil's temp was about 60C!) 60C means that the AW additives were only starting to function!

At the 15mins point the engine's core temperature was still about 20C below its normal core temperature and the oil temperature was still well below the design figure of above 85C.

The 928 looses an enormous amount of heat via its aluminium structure and many people forget this!

Perhaps the best way for you is to consider this;
a) start car and after 15secs run it at about 1000rpm for a minute or two then shut down
b) then, when you become "alive" again do your "drive like hell bit" as usual a few hours later

A lighter "W" synthetic oil such as 5w-40 would seem to be much better for you> if you wanted to gently clean the engine and convert to a synthetic oil then the castrol RX Super mentioned above is an excellent staring point. A 3k OCI using RX Super and a MANN filter will certainly do the job

One reason for pitting on camshafts in low uitilised engines is the type of oil used. Mineral oils do not fare well in this regard and HDEOs especially synthetics probably perform the best

Normy, I hope this helps and I do not want to display any "2c experts's arrogance" in my posts

Regards

Glenn M

Doug,
My NAPA in Maryland can only get the Delvac 15W40 which is CH-4, they told me it was synthetic. Nearest distributer is 80 miles away for 5W40. Am I better off with the 5W-40 SUV oil?

Thanks for all the time spent so we can keep our P cars running smooth!

Glenn

jpitman2

Normy, My car is also a lightly used one - once a week, an hour at best, interspersed with runs into work in heavy traffic once a month maybe. Recently changed to Delvac based on Doug's experience and advice. I didnt have any real idea what the POs oil change regime was, so I went onto a Castrol dino initially for a couple of short change intervals, then a semi synthetic for ~3k miles, and then Delvac 5w-40.
My regime is to start it, back out of the garage, pause while I get belt on, open sunroof, set radio/cd, get all settled in, then I stay under 3k until I see normal temp on gauge, then have what fun I can given speed limits and traffic. The 928 is one of the fastest warming up cars I have known - this may be a function of the gauuge calibration, but its time to normal indication is still very quick. The only times I have ever let it idle for any length of time from cold is when I am testing a problem like CIS pressures, WUR problems etc, or after TB/wP change - if I do it in current garage, the smoke detector will go off after 1 minute and drive everybody nuts anyway.
jp 83 Euro S AT 49k

Doug Hillary

Hi,
Glen - the Delvac 15w-40 rated CH-4 is probably NOT suitable for your car. It is NOT a synthetic oil
Mixed fleet oils will ALWAYS have a dual rating similar to this - CH-4/SJ. A single diesel rated oil should NOT be used in petrol engines

There is still mystery, misinformation and mindsets in the lubrication field. Even at Oil Co Rep and Distributor/Retailer levels too - it always amazes me after nearly 50 years involvement!

The correct Delvac oil is Delvac 1 5w-40 which will be rated CI-4/SL
In NA Mobil sell a another slightly reformulated version called Mobil 1 SUV 5w-40 and this oil is a fully synthetic oil suitable for your car too. This will be rated a little differently than above but should have both ratings

John P - Hi John, yes under normal running load the 928 will get up to a reasonable temperature quite quickly. It usually takes about 20-30mins to get all fluids up the normal operating equilibrium - depending on the ambient and operation of course.
I am sure you will let us know how Delvac 1 5w-40 works for you. Expect about a 0.5-1bar loss in OP when hot which is really what you want to see as it actually confirms better lubricant flow and cooling
John, IMHO your changeover routine was perfectly executed considering you did'nt know what the PO had been doing

Regards

JPTL

Glenn,
Hmm. 80 miles north by any chance?
I'm not quite 80 miles from Lex. Park, but pretty close. If the distributor has the correct oil that Doug refers to at a reasonable price, I'll go in on some & maybe make the pilgramage worthwhile for one of us. I'll use the 5w-40 Mobil 1 that I've amassed for my other vehicles. That 15w-40 that you mention was at Costco for a while in gallon jugs. The price was really good for what it was ("Super 1300" CH-4). I bought a couple of jugs and I ran it in my Explorer, but not my 928.
Not to get off topic, but how's that Stag? Not a common car. Is it keeping you busy?