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Engine Oils, S.A.E. Grades and API Classifications

I still get questions about engine oil from members, so I believe we should revisit the subject.  My recommendations regarding motor oil will pertain strictly to ETC-era Pontiacs and also Oakland from the same model years.  Pontiac engines used poured Babbitt bearings from 1926 through 1934 and the recommended grades of oil reflect the lack of precision tolerances in these bearings.  See the 1932 engine oil recommendation chart, and note that S.A.E. 30 oil is the grade you would want for summer use in these early engines.  Prior to the advent of S.A.E. grade ratings for motor oil, Oakland and Pontiac recommended oils by brand name in the owner’s manuals.  There were 2 lists, oils/lubricants for summer use and a second list of those acceptable for winter use.  Once the S.A.E. standards were established, the motorist could be reasonably assured the oil they purchased would flow as advertised.  It was still up to the oil company to provide a quality product in all other respects.  Read the opening paragraph of the 1932 oil chart.  A similar warning was included in every Pontiac owner’s manual through 1952, and I will have more on this subject latter.  
  The advent of precision insert bearings in 1935 allowed the use of S.A.E. 20 oil as long as the temperature was above freezing, (32º F).  The second engine oil chart dates from 1940, (next page) although its oil grade recommendations remained essentially the same through 1954, with 2 notable changes.  The first change came at the end of World War II, when the use of S.A.E. 30 oil at ambient temperatures of 90º F and above was dropped.  The second change was S.A.E. 5W oil, which was announced in Pontiac Service Craftsman News No. 9 S-242, dated September, 1952.  The recommendation of 5W oil for cold weather use first appeared in the 1952 owner’s manual.
  Once it became available in the early 1950’s, General Motors accepted the use of  multi-grade S.A.E. 10W-30 as a replacement for S.A.E. 10W, 20W and 20 grade oils in all their automobile brands retroactive to 1935.  These new multi-grade oils were formulated to meet the highest API service classification at that time, “For Service MS” or “For Service MS-DG”, as were the new 5W oils.  The other 2 API service classifications in use at the time were ML and MM.  These API (American Petroleum Institute) classifications were relatively new in 1952.  Prior to the implementation of API classifications, it was up to the refiners to grade their oils as “regular”, roughly the equivalent of MM, and “premium” or “heavy duty” which equated with MS or MS/DG.
  Prior to the use of precision insert bearings in the mid-thirties, straight mineral oil was acceptable motor oil, assuming you used the proper viscosity, (S.A.E. grade number).  In the early API classification system this is ML (motor light) oil; and in our current API nomenclature, it is API-SA oil.
  I do not recommend using API-SA oil in any vintage Pontiac or Oakland from the ETC-era!  It is straight mineral oil with no requirement for improving additives.
  The advent of precision bearings, higher engine speeds and more horsepower output all conspired to require motor oils better than straight mineral oil.  A basic additive package was developed consisting of an anti-foaming agent, anti-scuffing agent and anti-corrosion protection.  By the late 1940’s refiners referred to these oils as “regular” grade motor oil; the early API classification was MM (motor moderate) and the current classification is API-SB.  This is the minimum classification of motor oil that I recommend you use.  If you believe in using non-detergent oil in your Pontiac or Oakland, be sure it meets the API-SB classification; some non-detergent oils are only rated API-SA.
  Motor oil technology advanced dramatically during the war and motorists reaped the benefits almost immediately after.  Detergent and dispersant additives were added to motor oil to minimize the formation of deposits and insure contaminants were carried away when the oil was drained from the engine.  There were also extreme pressure anti-wear additives, which were especially necessary in the new crop of high-speed overhead valve engines coming out of Detroit.  The final additives to appear were the viscosity index (VI) improvers.  These additives permitted a single oil to flow as S.A.E. 10W oil at low temperature and as S.A.E. 30 at high temperature.
 These new oils were referred to as “premium” or “heavy duty” motor oils.  The increased production of Diesel engines for trucks, buses and railroad locomotives also forced refiners to improve motor oils for use in these applications.  The API classification equivalent for gasoline-only engines was MS (motor severe) and for either gasoline or Diesel engines, MS-DG (motor severe/Diesel general).  The oldest current API classification you are likely to see today is API-SJ which dates from 2001; the newest current classification is API-SM, and this is the oil that caused the ZDDP controversy over the past year or two.

    I want to give you some background on API oil classification to better understand what is going on with motor oil.  The early system came into being in about 1952.  API established standardized testing to insure consistent quality for motor oil.  As with the S.A.E. grade system of the early thirties, once established, the motorist could purchase any brand of motor oil that met the manufacturer’s requirements for S.A.E. grade and API service classification and be assured the oil was suitable for the car.  The 1953 Pontiac owner’s manual was the first to specify oils under the early API designations of ML, MM, MS and MS/DG.
  The current API classification system is split between S (service) and C (commercial) categories.  Some mistakenly believe these letters to stand for Spark and Compression (ignition) but that is incorrect.  Oils intended for “Service” are formulated and tested for engines that are frequently shut off, possibly for days at a time, and could see any combination of low and high speed use; essentially the family car.  The necessary characteristics include all around good performance when cold and also corrosion resistance due the possibility of water in the oil from short trips in freezing weather.
“Commercial” oils are formulated and tested for engines that are rarely, if ever, shut off.   The requirements for oils used in police cars, taxicabs and semi-trucks are certainly different from what you need for either the family car or your vintage Pontiac!  These oils are tested to resist thickening, foaming and in the case of Diesels, the ability to hold large concentrations of particulate soot in suspension without a change in viscosity.
  Prior to the current SM classification, all previous S-category oils included all of the essential properties of their predecessor.  In other words, a 1971 Pontiac required API-SD oil to meet the warranty requirement; when API-SE oil came out in 1972, it was suitable for all new cars, plus it met or exceeded all previous requirements.  Putting API-SE oil in your new 1971 car could do no harm; putting API-SL oil from 2004 in your vintage 1971 Pontiac today could do no harm.
 The change in API-SM oil was a reduction in the level of ZDDP, a reduction…not complete removal.  ZDDP is essentially a zinc-based, extreme pressure anti-wear additive that has been in use since World War II.  It is particularly effect in preventing camshaft / valve lifter wear on conventional “flat-tappet” applications.  The amount of ZDDP in SM oil was reduced because when burned in the engine, it would poison the catalytic converter, increasing tail-pipe emissions.  Since new engines are using “roller” camshaft / valve lifter technology, only minimal amounts of it are required.  According to some sources, even high-performance engines of the muscle car era are OK with SM oil, assuming they are original or rebuilt to original factory specifications.
  People got into trouble with SM oil when they tried to use it V-8 engines with high performance cams and stiff valve springs.  There is now evidence to show that even in many of these applications, once the camshaft and valve lifters are properly “broken-in”, API-SM oil offers adequate protection to prevent premature wear.  It is the process of breaking-in a flat tappet camshaft that requires great care and a heavy dose of anti-wear additives.
 None of this hullabaloo over SM oil applies to ETC-era Pontiacs or any Oakland automobiles!  Even as late as 1954, Pontiac permitted the use of MM (SB) oil for “normal” driving.  Normal driving was primarily around town use, with occasional highway trips.  If your driving was primarily high-speed highway travel, then MS or MS-DG oil was recommended.  Our flathead engines do not impose the kind of loads on the camshaft / valve lifter to worry about the use of API-SM oil of the proper grade.
  In the past few years, “high mileage” oils have appeared on the market.  If you go online to various oil company sites, you will learn these oils typically have extra levels of additives to prevent sludge and varnish formation, plus softening agents to keep synthetic rubber seals pliable and reduce oil consumption.  Most refiners also state that their high mileage oil is formulated to better resist thinning, a further aid to reduced consumption in an engine showing piston ring or cylinder wall wear.
  I was using Pennzoil 20W-20 oil in my car until they quit making it, now I use “high mileage” 10W-30 oil.  I have always used modern oil in my vintage cars, the only thing I use non-detergent oil in is my air compressor; it was built in 1950 and that’s what the manufacturer called for.  I maintain my cars for 3 season driving, so cold weather starts could be an issue.  If I owned a pre-1935 Pontiac and only drove it during warm weather, I would use modern S.A.E. H. D. 30, for 3 season driving I would be back to using 10W-30.  I would prefer to see the engine “use” some oil rather than switch to a higher S.A.E. grade number, and I’ve actually seen the oil consumption decrease in my ’53 since I first got it.  I drive my car about 20 miles before draining the oil, and I usually leave the plug out for half an hour so it drains thoroughly.
  If you are adamant about using non-detergent oil, be sure to use API-SB oil.  Kendall offers SB oil in 10W, 20W-20 and 30 S.A.E. grades; these 3 grades cover all ETC-era Pontiac and Oakland automobiles for summer or winter use.  Your local N.A.P.A. store probably stocks non-detergent S.A.E. 30 that meets API-SB specifications.

  In researching this article I was surprised to find that Lubriplate®, well known for their grease products, offers Super HDS Motor Oil.  This line of oils meets API-SJ/CF classification in 5 S.A.E. grades: 10W, 20W-20, 30, 40, and 50.  I plan to look for a Lubriplate distributor in my area and check on pricing of this oil.  It appears to me that Lubriplate is catering to the old car hobby, in my recent research I have not found another oil company offering such a list of oil grades.  Pennzoil, Quaker State and Valvoline, just to name a few, used to offer all these grades and no long do.  These are effectively obsolete grades, new cars all demand multi-grade oils to meet warranty or fuel economy requirements, plus the convenience of using the same oil summer or winter.
  One of the reasons I was using Pennzoil 20W-20  in my car was the fact that it carried more hot oil pressure with 20W-20 than it does with 10W-30.  If you check the API circular logo on a bottle of SM 10W-30 you will find that it meets the energy conserving requirements too.  You will not find this on 20W-20 oil, it is too thick.  This is another reason  that straight grade oils are obsolete, with governemnt regulations for fuel economy and emission, car manufacturers' are building engines  with extremely tight tolerances.  The required oils are commonly 5W more so than 10W, and 0W is available in the synthetics.
  If I can find a local source for Lubriplate oil, I will probably switch back to 20W-20 and see how it performs in my car.  I know what to expect from 10W-30, it might be interesting to see if I record any reduction in fuel economy of a long trip.
  I contacted Lubriplate about their non-detergent oil because the product data sheet was several years old, unfortunately their oils are all API-SA classified, so I do not recommend using them.
  If you go to the Kendall website, the data sheet for their non-detergent oils shows small amounts of zinc.  This would be consistent with the anti-scuffing properties required of SB oil.
  We have covered a great deal of information this month on the subject of lubricating your vintage car. The possibilities are nearly endless because there are so many products on the market to choose from, and most of them are more than adequate to the task.  I believe the most important point to be made on this subject is not about the products you use, but the fact that you take the time to thoroughly inspect you car!  The lubrication chart serves as a helpful reminder of the dozens of items that need to be checked from time to time.
  It is common knowledge that Andi and I travel often in our ‘53 Chieftain; people are constantly coming up to us and expressing surprise that anyone would travel such distances in a 50 plus year old car.  Granted, I worked on cars for 25 years, but we still would not be traveling those distances if I thought the car was about to break-down.  I keep a close eye on the car whenever we have it out.  The reason we keep track of fuel economy is to have warning of impending trouble, and that applies to more than just the engine.  If the transmission was beginning to slip excessively, it will show up in the fuel economy.  The same is true if a brake begins to drag due to a bad wheel cylinder.
  I hope to have our ‘40 Pontiac back on the road before too long, and we will drive it just like we drive the ‘53.  The car was certainly capable of long distance travel when new, but we will work up to  long trips by driving close to home in the beginning. We all have to build confidence in our older cars, and check them carefully for any signs of trouble.

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Engine Oils, S.A.E. Grades and API Classifications