RDS928S

Gent's

dont forget the heavy 15-50,20-50w oils rob significant power.
Check out the www.Redline.com web site. They have some nice dyno info on
V-8 motors that show significant HP gains with 0-30,0-40 weight syns.
The new light syns are more than adeqaute for everyday street use.

RDS

macreel

Mark... Look at Blackstone Labs... $20 a shot; i.e. about 3-4 oz in a bottle, baggies etc
they send you (free). The analysis has the price tag. They send you an e'mail report
followed by the paper. Good folks, good info. Pretty prompt, too.


G'luck

Doug Hillary

Hi,
thanks for the feedback. I'll be presumptuous and offer these comments;

RDS928S (Rich) - Mobil 0w-40 is one of the Worlds great lubricants. It is a factory fill at Benz, Porsche and a number of others. I use M1 0w-40 in my CLK Kompressor Benz
It is the Porsche and Benz fill at Dealerships here in OZ (and elsewhere) - as it should be!
The Tri-synthetic formulation has been superceded twice and is now at the second version of the "SuperSyn" formulation and at the latest "SM" API quality rating.
It has many engine maker's Approvals and formal Listings
Personally I would use Mobil 1 Turbo Diesel 5w-40 (Delvac 1 5w-40) instead of Mobil 1 0w-40 in a 928 unless the ambient is regularly below -15C. The reason? - well, the 5w-40 oil mentioned has a higher HTHS viscosity at 150C - 4.1cSt versus 3.6cSt

Roger - your question has already been answered wisely (great Chris!)
If you want to use a 15w-50 version of M1 it is the "EP" model. This oil is a little more robust that M1 Turbo Diesel 5w-40 in that it has a HTHS viscosity of 4.6cSt at 150C (versus 4.1cSt).
The benefit of the 5w-40 oil is that it has a "better" formulation (20+% Group 5 advanced ester content) and its higher TBN makes it ideal for low use/high storage time vehicles
M1 15w-50 is available in OZ to special order or as Motorcycle oil - our "heavy" M1 is 5w-50 which is the worldwide and Porsche Approved and Listed version. It is probably the Worlds best selling Mobil 1 lubricant

Andrew - yes, Shell Rotella T 5w-40 is a Group 3 "mixed fleet" synthetic lubricant. It is "similar" to the factory fill lubricant use at Porsche for the last few years of 928 production! Shell make an excellent range of lubricants!

Jim B - thanks! An oil tanker will moor near your door soon. 30 000 litres just for you!!!

Heinrich - I'm pleased that Delvac 1 5w-40 has been good for you!

Gretch - what do you use in the Harley? - Bourbon???

Bill - Delvac is a Commercial range of ExxonMobil lubricants. They hav a long and respected history, Delvac 1 5w-40 has been on sale for nearly 20 years. Only a very few Delvac engine oils are suitable for use in petrol engines. These are the "mixed fleet" formulations as follows;
Delvac 1 5w-40 full synthetic (the subject of this thread)
Delvac 1300 15w-40 mineral oil (a very good product)
In Australia Delvac MX 15w-40 is also a "mixed fleet" oil

Bill, it is always unwise to use a "diesel only" engine oil in a petrol engine due to the complex nature of some formulations and the risk of engine damage caused by high sulphated ash deposits and etc

Mark - Bill's and RDS928S (Rich's) comments about using a 20w-50 oil (and Amsoil) are very relevant. We even have one Service Provider here in OZ who actually recommends and fills 928s with a 25w-50 obsolete specification mineral oil

I'm sure the UOA results from the Lab test (Richard S's link to Blackstone is a great recommendation) will be of interest to us on this thread

Regarding viscosity, the lower part of the multi numbers (eg 0w-??) Is really only an indication of the oil's performance at low temps. It does NOT play a part in indicating the oil's normal operating temperature performance.
Porsche state that a 5w-40 is suitable down to -15C and a 0w-40 should be used below that. You can use the 0w-40 all year round "anywhere"in their perspective. As the two oils heat up they approach near equal viscosity from around 90C (M1 0w-40 and Del 1 5w-40). at around 90C.
In a 928 with the oil's temperature at around 90-93C (which is quite normal) the ?w-40 lubricant still has the viscosity of a ?w-50 oil

A 928 engine in particular should use a 5w-?? synthetic oil to ensure adequate cold start oil flow (especially to thrust bearings and in the valve train) and quick filtration, just as the Porsche Engineers intended! And, as they did themselves as the 928's factory fill!

Please note that I do note have any relationship with any Oil Company and strongly believe in using Porsche's Approved and Listed oils - or better!

macreel

Doug... a while ago you asked for my test results. Here:

Oil Condition (13,921 mi);

Viscosity OK - 77 @210 degF.(Virgin oil is 92)
Water content OK - trace
Sodium content - 54 ppm
TAN OK - ??
Fuel - 1.5 ppm
A'freeze - 0

Lab. UOA Report Summary;


Translated status "Suitable for continued use"(but I changed
so now using Castrol Syntec 5W-40)
Last Report: NA

Elemental (& wear metal) Analysis (in parts per million - "ppm");
Details of the following columns;
Column 1- current UOA result (my comments follow in brackets, Doug H.)


Iron 18
Aluminium 9
Chromium 6
Copper 27
Lead 8
Silicon 5
Calcium 1460
Tin 0
Potassium 1
Magnesium 52
Phosphorus 628
Zinc 764
Molybdenum 29
0= Ni, Mn, Ag, Ti, B, Ba

There you have it.

Bill Ball

Doug:

Your answers are always a masterpeice, but like good art, they take some training to really grasp. You pointed out Delvac 1 5W-40 is what I should be looking for among the Delvac line. That's clear. You add that 40 and 50 Mobil synthetic oils have the same viscosity at 90-93C. I had low oil pressure at idle with Castrol Syntec 5W-40 at the end of an open road race. I don't see that with M1 15W-50. So, I have gone back to that. The engine was very hot and the oil may have been above 93C. You comment that M1 15W-50 has higher cSt at 150C than Delvac 1 5W-40. This leaves me a bit confused about the high temperature viscosity and the oil I should be using.

heinrich

well ....... Godzilla made 299rwhp and 299rwtq with Mobil One 15W-50

fabric

I've also observed some low oil pressure at high temps in city traffic with the A/C on. Fine on the highway with good air flow, but once on surface streets I was not getting much above 3 bar. This was in 90-100F ambient temps.

Doug Hillary

Hi,

macreel - thanks for the UOA. Some more details please.
a) What oil were you using? - some details (Calcium level etc) suggest it may have been Delvac 1 5w-40.
b) Was your oil in use for 13921 miles?
c) What Lab did your test for you?

Bill, just a little bit of confusion.
I commented that both M1 0w-40 and M1 Turbo Diesel 5w-40 (both SAE 40 oils measured at 100C) have the viscosity of a SAE 50 oil (say M1 15w-50) at 90-93C.
The SAE 50 oil is thicker at 100C than both of the SAE40 oils mentioned at 100C
And yes, M1 15w-50 (4.6cSt) is slightly more viscous than the M1 5w-40 at 150C (4.1cSt) but I suspect that the lighter oil is more robust near 200C but I cannot substantiate this

Castrol's Syntec 5w-40 has a low HTHS viscosity of 3.5cSt at 150C and 14cSt @ 100C
This was probably the prime reason you saw a low OP at a very hot idle. I would not use this oil in a 928! As I said earlier, I would always want my HTHS vis. to be around/above 4cSt!

As Heinrich has indicated, M1 15w-50 will show a higher hot oil pressure than both the M1 SAE40 oils. However the oil's FLOW rate will be the same for all viscosities
Typically, oil pressure (OP) at a hot idle (after at least 30minutes) will be around 1.5 to 2.5bar with the SAE 40 oils. As well the HOT OP typically should be around 4bar at 1400-1600 rpm and MUST be above 5bar at around 4000rpm (variously from 5bar @5000 to 5bar @4000 rpm (oil temp 80-100C)

Viscosity is a very complex subject. Two oils of similar viscosity of say SAE 40 (one mineral the other synthetic) will have different flow rates. The synthetic oil will inevitably flow better than the mineral oil. As well a fully synthetic oil will usually flow better than a semi synthetic (eg Castrol Syntec) but may show a lower oil pressure in each case

People get nervous about the OP gauge reading lower than 3bar at a hot idle - mostly this is not justified as FLOW is still maintained. As long as you have at least 1bar and the OP quickly recovers to around to 2-2.5 bar, all is well. It is worth checking the oil cooler thermostat if you suspect the OP is too low!

Bill you can use M1 15w-50 with great confidence!

Chris - if you lose a few revs at idle with the A/C on the OP will go down in "sympathy".
My OP off the non clinical gauge is:
Hot idle (about 675 rpm) - 2-2.5bar
Hot 1600 rpm - around 4bar
Hot 2000 rpm - around 5bar

Chris - are you a road racer or a triathlete???

Regards

mark kibort

will do thanks!
MK

Bill Ball

"Castrol's Syntec 5w-40 has a low HTHS viscosity of 3.5cSt at 150C and 14cSt @ 100C. This was probably the prime reason you saw a low OP at a very hot idle. I would not use this oil in a 928! As I said earlier, I would always want my HTHS vis. to be around/above 4cSt!"

Well, that nails that down! THANKS! And the rest of the reply helped me see a number of things more clearly.

hacker-pschorr

Todd,
this guy:
https://rennlist.com/forums/928-forum/292299-a-look-into-todds-garage-7-and-5-5-liter-boosted-motors-in-the-making.html

Has been running L&E http://www.le-inc.com/ 20w-50 non synthetic in every motor he has ever built for his car - it's even driven in the winter (between blizzards, when the roads are clear). He has yet to experience any lubrication issues on his motor and supercharger.

Chuck Schreiber

Roger,

If you are having so much trouble getting Mobil 1 and have to drive to FT. Worth to get it, why not try Royal Purple 20W 50? Wylie will deliver it to your door "with a discount". Leave a check in an envelope. It's like getting Milk from the milkman!

I used Mobil 1 15W 50 for 7 years. Gave RP a try and was much happier with it. Car runs smoother and quieter, oil pressure stays consistantly higher, Wylie delivers it for free. Can't beat it with a stick!!

fabric

Thanks for the follow up Doug! That's about what I was seeing, hot idle seemed normal, but my hot OP at 2000 rpm was still around 3, and it didn't go much more at 3000 rpm, at which point I stopped and tried to keep things low till I got home. I would blame the gauge, but with the ambient air temp more moderate now, things are just like normal, and I was fine on the highway. So things appear to be fine except in high temp, low air flow conditions. I've checked all the obvious - both fans are workign (they weren't at one point, but I had general temp problems then), and the flaps are permanently open.

I'm a road and track racer, that's my faux aero position. I haven't actually raced on the track much lately, but that's where I got my start. The Aussies have churned out quite a few excellent road and track riders over the last 10 years, it's quite impressive. You ride as well Doug?

Bill Ball

He's running his own formulation. As Doug said, the standard viscosity numbers don't tell the whole story with various oils. However, I can't find a 20W-50 formulation on his website. He has a 10-50. I'd run that.

macreel

Doug... answers to your ??s :

a. oil ? beats me. The car came with it -mech never would tell me.
b. all 13,921, yes. (odd, that I changed to an oil you'd not use !)
c. lab = Blackstone

My hot OPs are the ~same as your listed values in response #38.

G'luck.