Doug Hillary

Hi,

This Oil Condition Report (Used Oil Analysis - UOA) is the eighth and final. It may be of interest to those who have followed the previous seven reports over the past almost two years
The oil and filter were NOT changed at this point as ExxonMobil's Lab. report OK'd the oil for continued use. It will be changed about one month from now at Porsche's prescribed maximum time limit of twelve months or sooner if the distance covered exceeds 12k miles

This is the fourth UOA on Mobil's Delvac 1 5w-40, a fully synthetic commercial "mixed fleet" HDEO (heavy duty engine oil). This oil has both the highest diesel/petrol ratings and is the latest API "CI-4/SL" rated "mixed fleet" diesel engine oil. It also exceeds ACEA's A3 and B3 ( E3, 4, 5 & B4) ratings. It is suitable for high performance petrol engine vehicles and meets the 928's viscosity and quality requirements stated in the Owners Handbook

Details:

Car - MY89 - 928S4 Auto
Speedo - 84557 miles (136163kms)
Oil - Mobil Delvac 1 - 5w-40 full synthetic - API rated as "CI-4/SL"
Oil/filter change date - 09/20/03 (OEM "MANN" filter used )
Distance since oil/filter changed - 11848 miles (19079kms)
Time since oil/filter changed - eleven+ months
Oil used since oil/filter change - nil (still near "FULL" mark)
Date of this sample - 8/23/04
Distance since last UOA - 1545 mile(2488kms)
Time since last UOA - approx. four months
Use in this period (approx) - 10% town, 13% urban, 77% hiway
Avg speed in period - 44 mph (70km/h)
Fuel economy in period - 20mpg US (11.8ltr/100km) (24 mpg Imp)
Ambient in this period - from 35c high to -3c low Humidity in this period - 88% (highest)

Oil Condition - "use" factors;

Viscosity OK - 92 (excellent)
Water OK - 0.0%
Soot Index OK - 0.00
TAN OK - 3.7. (excellent) - Start 1.00 & Max allowed 8.9

Lab. Report Summary

ExxonMobil's rating now - "Normal"
Status-Excellent for continued use
Last Report - "Normal"


Elemental (& wear metal) Analysis;

Detail of the Elemental columns are:
Col 1 = this UOA (my comments in brackets)
Col 2 = averages of all eight UOA's
Col 3 = Oil Industry's "acceptable" max. wear rates (rounded) & not 928 specific

Iron 10 ( excellent ) [8] (( >100 ))
Aluminium 6 ( excellent ) [4] (( >30 ))
Chromium 1 ( excellent ) [<1 ] (( >30 ))
Copper 4 ( excellent ) [4] (( >50 ))
Lead 11 ( excellent ) [6] (( >100 ))
Silicon 5 ( excellent ) [8] (( >30 ))
Sodium 6 ( excellent ) [4] (( >10 ))

Note:
The elemental/wear metal rates are very low. All are around the previous averages and well below the Auto Industry's "acceptable" figures. This indicates that the rings, pistons, bores, cams, bearings and other major components are wearing at a very very low rate indeed
This is another "technical analysis" of why the 928 engine is so durable in normal use when using the Porsche recommended (or better) lubricants that are changed at Porsche's recommended servicing intervals

Oil Condition Summary:

The lighter 5w-40 viscosity oil has now been used for almost 12000 miles (19079kms) over about eleven months. During this time the car was driven above 100mph(160km/h) for some long periods in 30+C and at below freezing temperatures
This very high quality oil has contributed to the overall lowering wear rate trends and has caused the wear trend averages to fall accordingly
The oil will be changed in September according to Porsche's time - maximum 12 months use - recommendation, but the maximum distance may still be reached!

RENNLIST's 928 owners now have a very good baseline of UOAs from which to measure their own engine's wear and oil degradation rate trends. This will also assist those persons who race our engines.
A number of Labs. in NA do UOAs - but it is always better to use one that is well known

Regards

John Veninger

hacker-pschorr

Where does one purchase Mobile 1 Delvac?

Mark

Hacker - I've actually seen the DELVAC at Sam's Club! (tho - I do NOT recall if it was the synthetic or not).

I have been running Castrol GTS...NON-Synthetic. I've heard pro's and con's about switching to synthetic ("seals will start leaking")...anybody BTDT and care to comment??

hacker-pschorr

Mark, I've switched every car I own to Mobil 1 synthetic after I bought them. No leaks on any of them:

Audi - purchased with 140,000 miles
928 - purchased with 90,000 miles
944 - purchased with 86,000 miles
Scirocco - purchased with 110,000 miles

I'm not saying I don't belive what you state isn't possible, just hasn't happened to any of my current cars.

hacker-pschorr

From Mobil 1's site:

Mobil 1 vs. Mobil Delvac 1® for a Gasoline Engine

Q. I have read on the Internet that Mobil Delvac 1 oils may provide better performance in high-performance passenger-car engines than regular Mobil 1, since they meet CF-4 specs. What about using Delvac in gasoline engines, especially high-performance engines?

-- "Tribological", Richmond, VA

A. Mobil 1 formulas will deliver everything you need for your gasoline engine. In fact, during development, tests are run in both gasoline and diesel engines to demonstrate the superior performance of Mobil 1. Mobil Delvac 1, which is designed for heavy-duty diesels, meets most diesel engine oil specifications, and also meets API SL certification. And because Delvac 1 operates in a different environment – diesel engines run longer, generate soot and run hotter, it contains different types and amounts of additives than Mobil 1. Even so, Delvac 1 still meets API SL certification for gasoline engines, and because of its high performance, we would expect it to do a good job of protecting your gasoline engine. If you use your gasoline vehicle in "heavy-duty" service, Delvac 1 will provide many benefits compared to conventional oils. When compared to Mobil 1 performance, those benefits may not be as obvious, and in fact, Mobil 1 would be expected to outperform Delvac 1 in many gasoline applications.

ErnestSw

Doug,
Many thanks for the excellent information.
I've used Delvac in my GT for the last 2,000 miles. After the engine was filled I checked the level and confirmed it was correct. I ran the car on a local 1.8 mile 10 turn track for about 25 laps as part of a 1500 mile trip and discovered that I was down 2 quarts when I returned home. No leaks and no evidence of oil burning other than the level. The car was dynoed at 280 RWHP after the track event, which is exactly where it should be.
I realize that this is not an oil quality question, but any comments, observations?

WallyP

Yeah - Check the oil more often!

;-)

Nathan Valles

From previous private converation with Doug, I believe that "Mobil 1 5w-40 TRUCK & SUV FORMULA" is the same as "Mobil DELVAC 1" but repackaged into 1 quart bottles for gasoline engines. It can be found in any Wal Mart or Auto Zone store in the US.

Gretch

I converted my fleet to mobil 1 (delvac, for the diesels), in large measure due to Doug's research results and diligence in posting them here. Thanks Doug, you are a class guy.
Re: Availability of Delvac, I had to pester my local NAPA dealer to carry the Delvac, because neither he nor anyone else in town (several auto parts and tractor parts dealers) carried it. The local NAPA guy got me several gallons of the Delvac, and I pretty much clean him out of stock everytime I visit his store.

I run synthetic oil in 3 high performance automobiles, my hunting truck, two ATVs, my Harley, a John Deer industrial mower and two sleds (chaincase only). I run the Delvac in the crankcase of both of my diesel tractors. We flog the tractors pretty hard all year long, they cost a bunch, and I feel much better about using the Delvac in them. (BTW, they both leak gearcase (not crankcase) oil much worse than the 928 ever will leak crankcase oil). Tractors ARE NOT domesticted.

Doug Hillary

Hi,
thanks for the interest

Ernest - like Wally P suggests you will no doubt will be checking the level more often. Sometimes any oil left in during an oil change may dilute the new oil charge and burn off quickly - but not two quarts! Delvac 1 5w-40 is NOT known as a "burner" due to its base oil structure - its seems very odd to me. Please keep us posted. As you can see from the report my car uses none (neither do my other vehicles) and my OTR trucks have averaged 1ltr/6k kms over millions of kms

Nathan - you are correct - Mobil 1 SUV 5w-40 is "supposedly" the same stuff and shares an almost identical virgin oil analysis result. ExxonMobil realised they had an excellent product that was unknown to M1 users and light diesel SUV owners. Hence the two name marketing
Delvac is the name of ExxonMobils huge Commercial engine lubricant range of both minerals and synthetics. Delvac 1 is the synthetic stream!

Gretch - thanks!

It is unlikely that Delvac 1 (or SUV) 5w-40 will promote leaks and this is due to its base oil structure (esters). I would expect it may even minimise some due to the seal swelling additive content. I have changed a OTR heavy truck engine over at 800k kms without a problem. I expect that Mobil 1 SuperSyn won't either and this range of oils now has an excellent world wide reputation amongst Tribologists. Do not buy any old stock M1 "Trisynthetic" if you can get SuperSyn!

Many 928 owners are now using Delvac 1 5w-40 here in Australia (SUV is not sold here) and all users speak well of it.

Either of these oils (Del 1-SUV) are excellent in our cars - especially those that are not used very often. This is because Heavy Duty Engine Oils (HDEO) such as these have significantly increased additive protection against corrosion, oxidation and better deposit control in low/high temperature operation over petrol engine specific oils

I have just done some reasearch on the progressive warm up viscosity of oils in the 928 and it is very important to use those viscosities recommended by Porsche for the 928. A synthetic 5w-40 is one of those

One Service Provider here in Australia has been using a 25w-50 mineral oil in the 928s they service and I strongly advise not to use this (or a 25w-60) non approved viscosity of lubricant.

Castrol "R" 10w-60 an excellent full synthetic may be a good choice when racing to minimise oil consumption

I use the best of Mobil, Shell and Castrol's products as the case arises. As always it is a case of personal choice and the correct application of the available technology

Regards

Jim bailey - 928 International

Thanks again Doug for doing what no one else has done in the 928 community . Actually testing the oil to prove that there is no rational logical reason to change oil any more often than what Porsche recommended. If a "professional" shop is recommending changing your oil much more often they simply want your money or are terribly misinformed . For high RPM racing applications there May be better specialized oils whose additive package MAY resist foaming better than normal synthetic brews but there is only subjective data from several "racers".

aaron3

Doug,

Thanks for all your good work. I'm interested in the statement about the mineral oil 25W-50 and 25W-60 oils. Is the concern the high viscosity or the fact it's mineral oil? I know alot of racers here use Amsoil 20W-50. I use this in my 928 (non-racer), and like it. I have no oil consumption and the car runs seems to run quieter. I did have some oil consumption with Mobil 1. I'm interested in your thoughts.

worf928

My '91 GT uses 1/2 quart of oil per run session. That's two quarts per day.

As Wally said - check your oil more often.

I check my oil after every run and top it off with another 1/2 quart.

Look at it this way - 4 track days and you've changed the oil.

Doug Hillary

Hi,
pleased to offer comment as requested

Jim B. correctly referred to special brews used in some racing situations and of course this is very true. Shell for instance have a Chemist and a Blender at every Ferrari F1 outing practice and etc. Oils are analysed and blended on site according to the rev range anticipated, fuel blend, temperatures, length of race and etc etc. A very complex matrix indeed!!

For the average weekend racer it eventually comes back to a few factors and one is very critical - High Temperature High Shear (HTHS) viscosity which is measured at 150C to a set "destructive" type of protocol. Porsche published a minimum HTHS for their "Approved" oils at 3.5cSt
In weekend racing I would want well in excess of 4cSt and perhaps up to 5+cSt according to the then increasing power loss involved. Amsoil and some others have this viscosity and additional quantity of additives such as zinc in various guises. The latest Group 5 Mobil 1R 0w-30 has a HTHS vis. of 2.99cSt - under Porsche's minimum of 3.5cSt. This oil has VERY advanced additives and seems to blow some Tribology theories apart by practical results
Other slightly less critical issues are the NOACK volatility measurement and the oil's resistance to foaming - Porsche have a special test protocol for this "bubbles in the oil" bit!

The HTHS viscosity becomes a problem of power loss once above about 4.5cSt and an oil that is too viscous (thick) can create problems of wear and bearing failure

Oil forms a hydro-dynamic "wedge" within the crankshaft/bearing interface (it's the same in other similar type bearing areas - cams etc) and this can form a structure that is at least as strong as the material it is supposed to be lubricating. You can anticipate the problem - a reduced oil flow causing rapid temperature rise and abrasive wear! Oil pressure has very little affect here as the pressure within the interface is very very high indeed - much higher than the oil pumps - oil FLOW is critical however!

This principle applies to using non-synthetic oils with viscosities like 25w-50, 25w-60, 25w-70 and the likes. This is especially so in a 928 engine where the operating oil pressure is beyond 4bar and could be at 8-9bar. These oils have poor cold temperature flow characteristics and cause extended relief valve actuation and actuate filtration media by-pass for very long periods

As an example Valvoline's GP50 25w-50 mineral oil sold here is almost four times thicker at 10C (50F) than Delvac 1 5w-40 synthetic. At the critical 50C (122F) oil temperature point it is still twice as thick! The critical 50C is reached at from 6-10 minutes in the 928's warm up cycle (if you are using the OEM coolant thermostat with an 81-85C crack point) and is about 20C (68F) behind the coolant temperature at this point!
This of course does not register the benefits of the far better oil flow characteristics of a full synthetic oil

The anti-wear additives in most engine oils commence to seriously function above about 45C and so a combination of all of these and some other factors make using a Porsche recommended viscosity engine oil very important indeed

Mark N - Your use of a recommended viscosity 20w-50 synthetic oil in normal use is correct only if the temperature range anticipated is correct! Porsche advised that as a mineral oil it is suitable for from 5 to 100F. Group 3 synthetic 5w-40 or 5w-50 oils are suitable for the <-20 to 100+ range. Group 5 synthetics do it all better!

Dave C - good points!

Remember it is really not the brand of oil that matters it is its specification

Regards
Doug