Oil type

[CJHenderson]

Unable to find oil specs. What oil viscosity should I use on an engine that has 102,000 miles on it.

[jameshoward]

Ah, joy, the old oil debate. It's been months. I'll put the kettle on.  

(Incidentally, have you tried the search function? It'll provide you with masses of inconclusive information, suppositions, depositions, and contrary advice. FWIW, I use a 20W50 classic car mineral oil, high in zinc, with 'seal conditioners' that's relatively inexpensive, but which the car likes most out of all the ones I've tried. My engine has slightly fewer miles than yours. If you aren't running a synthetic, I'd recommend that whatever you read here, you shouldn't change to one; stick with roughly what you've got).

[Norm]

As James already pointed out there is enough information on this subject already posted that you can stay entertained with research for days.

Since you are in the US and did not mention any particular problem that you are trying to address with your motor oil choice (a bad idea by the way) you should consider a Heavy Duty Engine Oil designed to meet specific wear performance specifications.  In the US, this class of engine oil is referenced by "C" type by the American Petroleum Industry (API).  The latest approvals are for CJ-4.  For viscosity, one of the most common HD Engine Oils is 15w40 and should work well in your engine.  

Automotive Oils are classified by API with an "S" and the current designation is SN.  The problem with current automotive engine oil specifications is that they are designed to meet demands of today's modern engines and have actually reduced the amount of anti wear additive (the most common AW additives use zinc) to protect sensitive emission equipment.  If for some reason you prefer an automotive oil, Older "S" approved passenger car engine oils are better suited to our 50 year old cars.

James's use of a classic car 20w50 oil is wise since it provides an increased viscosity (vs. the original 10w30 oil specified when these cars and their engines were new) and "older" anti wear protection.  (new SN approval specifications can not be met with a 20w50 viscosity grade.  Most are 0w20 - 5w20)

Although there are many products and claims associated with engine oil additives, my personal belief is not to upset the formula that the engine oil producer (Shell, Exxon, Pennzoil etc.) developed to meet stringent API specifications.  But to each their own......

After a 40 year career in the Oil industry, all of it in the lubricant side of the business, I have learned that nobody knows everything that can affect your specific engine, but stick with a major brand and pay attention to the viscosity and API approvals and you should be just fine.

Norm

[GGR]

Norm,

I'm using Brad Penn 20w50. Is that good?

[Norm]

After reviewing their specifications for the High Performance 20w50 I would say yes.  But consider that the pour point (the temperature at which the oil will not flow) is -16F.  Their 15w40 has a pour point of -43F.  If your car sits outside or in an unheated garage, think about that before starting the engine on a cold winter morning.

Norm

Norm,

I'm using Brad Penn 20w50. Is that good?

[CJHenderson]

Thanks all, this helps greatly. Living here in Arkansas where we might see -10F once in a great while I'll go with 20W50 also I keep the car in the garage.

[Mike K]

I recently undertook an oil change on my 1971 280 SL, and did a large amount of research both on this site and other sources. I finally decided to go with a 20W50 oil and settled on the Elf Retro 2,
which if all the blurb is to be believed is specially formulated for engines built in 1960s -1970s. I have to say that since doing the oil change all seems fine and no oil leaks or oil seepage.

[mdsalemi]

I recently undertook an oil change on my 1971 280 SL, and did a large amount of research both on this site and other sources. I finally decided to go with a 20W50 oil and settled on the Elf Retro 2,
which if all the blurb is to be believed is specially formulated for engines built in 1960s -1970s. I have to say that since doing the oil change all seems fine and no oil leaks or oil seepage.

Elf and Total are not commonly available in the USA, (though not impossible to find); I hope that the essential lubricant content is where it should be. That would be the phosphorus and ZDDP. These specs were not listed on the 7 page brochure...

[garymand]

Norm, thanks for offering your experience.  I found a slide set from Mercedes-Club of America.  I am attaching it and a word doc where I have pulled the W113 pertainent info.  Would you take a critical eye to it and see how it agrees with your experience.  It would be nioce to get some consensus on this as most of us don't change our minds without overwhelming influence.  Disregard the date, the author didn't protect the date and stored as "Today's Date"

Specifically can you adress what the slides say about ZDDP and 20W-50

[garymand]

Norm, thanks for offering your experience.  I found a slide set from Mercedes-Club of America.  I am attaching it and a word doc where I have pulled the W113 pertainent info.  Would you take a critical eye to it and see how it agrees with your experience.  It would be nioce to get some consensus on this as most of us don't change our minds without overwhelming influence.  Disregard the date, the author didn't protect the date and stored as "Today's Date"

Specifically can you adress what the slides say about ZDDP and 20W-50

[garymand]

I ran into difficulty getting both to attach, here is the Slide set.

[Norm]

Thanks for posting this info Gary.  The presentation provides an excellent background for the development of modern engine oils and explains what is involved in engine lubrication.

I have some problem with the "absolute" statements concerning what will and will not work but allow that the author was attempting to convey his own beliefs.  Specifically, before I retired I had several conversations with product engineers from several major engine oil manufacturers as well as several engine oil additive suppliers about the suggested oil to use in my 66 230 SL.  All agreed that the use of a CJ4 15w40 Heavy Duty Engine Oil would serve my purpose very well.

To address your specific comments:

ZDDP is one of the most commonly used anti-wear additives for developing engine oils.  Be advised that it is not the only additive available and, as technology improves, I suspect at some point it will be improved and / or replaced.  ZDDP levels by themselves do not establish the feasibility of an engine oil.  The most consistent way to insure that a motor oil has wear protection is to check that the product meets industry standards for wear when tested as part of an overall approval system.  The only API products that are currently tested for wear as part of the approval process are the "C" grade heavy duty engine oils.  The latest approval being CJ4.  There are many ASTM tests that will indicate wear and or presence of ZDDP but, in my opinion, the API tests are the "gold standard" of the industry (at least here in the US) and I use them as the basis for my comments.

20W50 viscosity grade is not for everyone.  As I noted in an earlier post, depending on the pour point of a specific product, a 20W50 engine oil may not provide adequate lubrication at cold temperatures.  Please note that all 20w50 oils are not created equal so the real answer to the question, "Should I be using a 20w50 engine oil?" is "It depends on technical specifications of the product you are considering and the typical operating temperatures you will encounter in using your vehicle."  You should not conclude that a 20w50 engine oil suitable for use in warmer climates  will be suitable in cold climates.  (Example: Texas vs. Canada)

As an additional note, the choice of engine oil, while important, is not a "simple" decision (as noted in the plethora of information that is offered on this web site as well as many other sources) Engine specifications, product specifications, engine mileage, environmental conditions, financial considerations and even emotions are a part of what may be right for you.

For me, a HD 15w40 with API CJ4 approval works just fine.

Norm

[66andBlue]

Very instructive, thanks Norm!
What about synthetic oils for rebuilt engines, especially Mobil 1 15W-50 which seems to have some followers here?
   
Mobil 1 15W-50 synthetic oil meets or exceeds the requirements of:
API SN, SM, SL, SJ
ACEA A3/B3
Mobil 1 15W-50 is of the following quality level:
API CF
 
No "CJ" standard listed but "SN, SM, SL, SJ" and "CF". What is the difference?

See also:
http://www.mobil.com/USA-English/Lubes/PDS/NAUSENPVLMOMobil1_15W-50.aspx

[Norm]

Synthetic Oils only add a layer of complexity to your purchase decision.

"Meets the requirements of" is industry speak for "we don't sell enough of this product to pay for the expensive API approval".  When you read this kind of statement you are putting your faith in the hands of the product manufacturer.  Not much risk with a company the size of Exxon / Mobil. 

15w50 vs. 15w40?  I'm not sure an engine used in "normal" operating conditions would perform differently by any detectable measure.  For me 15w40 is just more available. 

Synthetic vs. Mineral Oil??  I think the synthetic is a better product from a stability point and allows for extended drain intervals but I change my oil once per year at around 1,000 miles, so the extra cost just can't be justified in my own mind.  (full disclosure: I use Mobil 1 0w40 in my 06 CL500)

The approval designations are progressive.  So SG was followed by SH etc.  As noted in the MBCA presentation the problem with "S" or spark designated engine oils in later approvals, reduced wear protection was allowed to achieve longer life for emission equipment (catalytic converters).  The logic was that while there was some level of wear protection, newer engines with better engine part tolerances could live with the lower levels of wear protection.  Newer approvals for "S" engine oil types are also evaluated on fuel mileage.  Which is why most are 0w20 and 5w20.  Lighter vis oils yield better MPG results!  The classic car owners were not served well by this decision but they constitute a relatively small part of the engine oil market.  This decision also resulted in a clear "Buyer Beware" status when purchasing a motor oil.

[66andBlue]

Norm,
about 5 years ago Michael Salemi provided some background on Mobil 1 15W-50: http://www.sl113.org/forums/index.php?topic=8522.msg73201#msg73201
It looked good because of its high Zn/Phosphorous content and its benefits for cars with "flat tappets".
Looking at the most recent information the company provides (May 2014) this is still correct. Interestingly among all the different Mobil 1 varieties only four are approved by Mercedes Benz, and 15W-50 is not among them and has only meager industry or ACEA approvals.
15W-50 is relatively easy to get here in CA and Walmart sells it 5 qts for about $23 (http://www.walmart.com/search/search-ng.do?query=Mobil%201&cat_id=0&facet=oil_viscosity:15W%20-%2050)