I am too a Rotella oil user and while pondering this thread on the Rotella diesel oil I went to my local GM dearlership, in Canada BTW, and they don't carry the GM E.O.S. assembly lube 1#1052367. What they do carry is AC Delco E.O.S. 1#992869. I didn't get any as I was unsure if it was the same product. The service manager assured me that it was and the GM stuff is only soild in the USA. The AC Delco is the Canadian version. I did a little digging on the net and found this article. After reading it I am now strongly thinking of going back and getting some. Any thoughts?
Mind you most of the following info is based more towards the auto industry but the part about Rotella Diesel oil is what I wanted to see. Hope this helps. BTW they do refer to the "boutique" oils which I guess are referring to the motorcycle oils.
Engine Oil Revisited
January 10, 2008
When I finished writing the first edition of The Shadow Owners Companion in the Fall of 2006, the prevailing
wisdom on motor oil was straightforward – make sure that your motor oil choice is rich in ZDDP (zinc dialkyl
dithiophosphate). Quite a bit has been written about this subject in club magazines since then including the
September 2007 issue of Self Starter from the Cadillac-LaSalle Club. This particular article has been mentioned
quite a bit in classic car circles recently. Chock full of good information, a few of the recommended oils are no
longer available, so here are some new recommendations and some additional thoughts on the subject as well.
Despite what you may think, the much-maligned EPA is not at the center of this maelstrom; rather, the North
American automotive OEMs have put pressure on the American Petroleum Institute (API) to release new
standards that lower the amount of phosphorus in motor oil. Phosphorus tends to reduce the efficacy of the
catalyst over time and with new mandates requiring emissions systems warranties up to 120,000 miles, reducing
the amount of phosphorus enables the OEMs to specify smaller (and less expensive) catalysts. These reducedspec
oils appeared on passenger car motor oils API rated SM and subsequently on diesel oils (like Shell Rotella T
and Mobil Delvac Super 1300) API rated CJ-4. The CJ-4 spec with reduced ZDDP became necessary as all
over-the-road diesels including tractor trailers came equipped with catalysts starting with the 2007 model year.
Why do we need an oil rich in ZDDP? This compound bonds with the ferrous elements in your engine and
provides a protective anti-scuffing function that prevents damage at the points that experience the highest metal
to metal pressures. For classic car engines with flat tappets, the major pressure point is where the cam slides
against the tappet face. These pressures are worst with engines that have heavy valve springs – for example,
those with aggressive cam profiles, large valves and/or high rev limits. Although our engines have big valves, our
cam profiles are mild and rev limits low. This puts our engines at less immediate risk than say a vintage Porsche
356 or 396 Chevelle. These engines accumulate cam wear in their engines at a faster rate, and we can thank
their owners for determining the root cause and finding a path to salvation.
This concern does not equally apply to all Rolls-Royce and Bentley motors. Roller tappet engines are at less risk
than their flat tappet brethren because the sliding friction is not as great. If you own a pre-war Rolls-Royce or
Bentley, you can relax as only the Phantom II, Phantom III, Wraith and (ultra rare) Mark V have flat tappets.
Unfortunately, almost all post-war Rolls-Royce and Bentley engines have flat tappet designs with the exception
the Silver Seraph and Green Label Bentley Arnage, Bentley Continental GT, and the New Phantom.
Given the relatively conservative design of our engines, having done an oil change or two with the new low ZDDP
oils probably will not have a discernible effect on the life of your already broken in engine. It’s somewhat like
drinking or smoking – the cumulative effect is what leads to health problems.
Rebuilt engines are an entirely different kettle of fish. The sporting and muscle car folks have experienced the
bulk of the problems with gross camshaft failures during the break-in period, with less than 1,500 miles on the
clock. If you are in the process of rebuilding an engine, oil selection is critical until everything is broken in.
How much ZDDP is enough? Most of the automotive pundits seem to agree that a proper motor oil for a flat
tappet engine should test with a minimum of 1,200 PPM (0.12%) by weight each for zinc and phosphorus.* The
now discontinued CI-4 rated Shell Rotella T and Mobil Delvac Super 1300 had over 1,300 PPM of zinc and
phosphorus. The discontinued SL rated versions of Mobil 1 all had over 1,400 PPM† for each. Unfortunately,
virtually all of the currently available oils with the latest SM or CJ-4 designations have zinc and phosphorus levels
at or below 1,000 PPM.
You can still buy “boutique” oils with the proper formulation. Depending on the manufacturer, these might not be
API rated. Quite often, they are labeled for motorcycle or racing use and usually available at speed shops and
through the internet. (Yes, it is legal to mail motor oil within the United States as the flash point is well above
200°F, which is what the regulations for flammable liquids require.) Based on lab tests tabulated by LN
Engineering, a manufacturer of performance parts for classic Porsches in California, choices for properly
formulated oils in relevant grades for Silver Shadow and Silver Spur era 6.23/6.75L V-8s are shown in Table 1.
* The 1977 SAE paper “Cam and Lifter Wear as Affected by Engine Oil ZDP Concentration and Type” written by
two GM Engineers provides plenty of data to support the assertion that 1200 PPM is “knee” in the curve of wear
rate vs. ZDDP concentration for flat tappet engines.
† With the exception of SL-rated Mobil 1 0W-40, which had ~1,000 PPM of zinc and phosphorus.
Brand Viscosity
Zinc
(ppm)
Phosphorus
(ppm) API Type
Street
price per
quart
Cost for
oil
change
Mobil 1 MX4T 10W-40 1542 1344 SG Synthetic $8.25 $82.50
Royal Purple
Max Cycle
10W-40 1222 4085 SJ Synthetic $7.00 $70.00
Redline 10W-40 1872 1440 SL Synthetic $8.00 $80.00
Swepco 306 15W-40 1476 1238 CI-4 Conventional‡ $6.00 $60.00
Royal Purple
Max Cycle
20W-50 3907 1458 SJ Synthetic $7.00 $70.00
Mobil 1 V
Twin
20W-50 1329 1949 SG Synthetic $8.25 $82.50
Brad Penn
Grade 1
Racing
20W-50 1250 Not tested SJ Conventional‡ $4.50 $45.00
Swepco 306 20W-50 ~1400 ~1200 CI-4 Conventional‡ $6.00 $60.00
Mobil 1 15W-50 Unknown 1200 SM Synthetic $6.00 $60.00
Table 1 – Currently Available Oils with Proper Amount of ZDDP
If you are looking to research other grades of oil, www.lnengineering.com/oil.html is a wonderful resource put
together by Charles Navarro. Most of the data in this document are based his lab results.
You can formulate your own oil by buying your favorite oil in the latest SM or CJ-4 spec and then adjust the ZDDP
content with an engine oil supplement. The choice favored in the Self Starter article is GM EOS 1052367. This
was discontinued during the summer and has been replaced by AC Delco EOS 10-106. The AC Delco product is
reported to have the same formulation as the GM, but I have not seen any lab results as confirmation. STP Oil
Treatment for four cylinder engines (STP Red) is a relatively inexpensive alternative. I would not recommend it
for the simple reason that you would have to use four bottles to bring your oil up to snuff. At that point 20-25% of
your crankcase would be STP rather than motor oil. (See Tables 2 and 3.)
Brand Size
Zinc
(ppm)
Phosphorus
(ppm)
Street
price per
bottle Comments
GM EOS 1052367 16 oz. 6221 5762 $16 Discontinued, but still available.
AC Delco EOS 10-106 16 oz. 6221 5762 $10-12 Replacement for GM EOS.
Assumed to be the same
formula.
STP Red 15 oz. 3932 2115 $2.89 Need at least four bottles to
raise zinc to 1,200 PPM in avg.
SM oil.
Table 2 – Additives with ZDDP
Average lab results Predicted results with EOS added
Amount of
additive to include
in 9-1/2 qt. oil
change.
API Rating Zinc (ppm)
Phosphorus
(ppm) Zinc (ppm)
Phosphorus
(ppm)
GM or AC Delco
EOS (oz.)
CJ-4 1014 819 1562 1339 32
SM 939 770 1495 1295 32
Table 3 – Average Zinc and Phosphorus Found in Currently Available Oils and How to “Correct” Them
I talked to world-renowned postwar Rolls-Royce expert John Palma at Palma’s Automotive Services in Audubon,
New Jersey. He indicated that they have seen cam wear issues on Crewe built Rolls-Royce and Bentleys and
that they use Justice Brothers Oil Treatment when performing oil changes at the shop. I have not found any lab
‡ highly refined parrafinic based petroleum oil, definitely not bargain basement stuff.
data on the ZDDP content of this product, but it may very well turn out to be an excellent alternative to AC Delco
EOS. Stay tuned.
There are many permutations and combinations of oils and supplements. Table 4 boils down the data into three
choices for 10W-40 synthetic lovers, two choices for 15W-40 diesel oil aficionados, three choices for 20W-50
fanatics and one for 15W-50 synthetic. Note that there are no Valvoline VR-1 picks on my list. VR-1 tested less
than our borderline for zinc at 1085 ppm and the VR-1 NSL (“not street legal”) version has even less at about 840
ppm. If you don’t like my choices, there’s plenty of data on the LN Engineering website and elsewhere to
formulate your own solution. And if you are wondering what my plans are: the 1939 Wraith and 1973 Silver
Shadow will be switched over to Swepco 306 15W-40 at their next oil change.
Oil API Viscosity Supplement
Cost for
9-1/2 qt.
oil
change. Comments
Shell Rotella T
(8-1/2 qts.)
CJ-4 15W-40 AC Delco
10-106
(32 oz.)
$54 Puts the ZDDP back into
good ‘ole Rotella.
Swepco 306
(9-1/2 qts.)
SJ/CG-4 15W-40 none $60 Very high quality
conventional motor oil, if
you swore by CI-4 Shell
Rotella T or Mobil Delvac
Super 1300, this is even
better. The BMW and
Porsche guys love this stuff.
Royal Purple Max
Cycle (9-1/2 qts.)
SJ 10W-40 none $70 Run full synthetic at a lower
cost than Mobil 1 options
below.
Mobil 1 High
Mileage
(8-1/2 qts.)
SM 10W-40 AC Delco
10-106
(32 oz.)
$83 One option for Mobil 1
enthusiasts…
Mobil 1 MX4T
(9-1/2 qts.)
SG 10W-40 none $83 Another option for Mobil 1
enthusiasts.
Brad Penn
Grade 1 Racing
(9-1/2 qts.)
SJ 20W-50 none $45 Brad Penn also offers 30W
break-in oil, for those of you
rebuilding older R-R six
cylinder engines. Both oils
highly recommended.
Royal Purple Max
Cycle (9-1/2 qts.)
SJ 20W-50 none $70 Run full synthetic at a lower
cost than Mobil 1.
Swepco 306
(9-1/2 qts.)
SJ/CG-4 20W-50 none $60 Very high quality
conventional motor oil.
Mobil 1
(9-1/2 qts.)
SM 15W-50 None $60 Exxon-Mobil recently
published the ZDDP content
of all their synthetic oils and
this one is the only one they
recommend for flat tappet
engines.
Table 4 – Total Cost of Oil Change (Minus Filter)
At Sherbourne Mews, we set out to publish a little niche publication on Rolls-Royce Silver Shadows and perhaps
manufacture a few unique automotive tools and the like. We didn’t set out to be in the oil business, but we are
happy to give it a try. As of Oct. 18, 2007, you can buy cases of Swepco 306 15W-40 and 20W-50 from us!
RH used the words sanity and forum in the same sentence. :rofl: 
