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2 The United States/North America Tripartite System

2 The United States/North America Tripartite System

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60,000 at –40

60,000 at –35

60,000 at –30

60,000 at –25

60,000 at –20

60,000 at –15

Low-temperature,◦ C,

pumping viscosity2 , mPa-s,

maximum, with no yield














Low-shear rate kinematic

viscosity3 mm2 /s at 100◦ C




3.5 (0W-40, 5W-40, 10W-40


3.7 (15W-40, 20W-40,

25W-40, 40 grades)



High-shear rate viscosity4 ,

mPa-s at 150◦ C, minimum

ASTM D5293; 2 by ASTM D4684 – note that the presence of any yield stress detectable by this method constitutes a failure regardless of viscosity; 3 by

ASTM D445; 4 by ASTM D4683, CEC L-36-90 (ASTM D4741) or ASTM D5481

From SAE J300, revised 11/07, with effect from 05/2008, supersedes SAE J300 of 05/2004

6200 at –35

6600 at –30

7000 at –25

7000 at –20

9500 at –15

13,000 at –10

SAE viscosity grade

1 By

Low-temperature,◦ C,

cranking viscosity1 , mPa-s,


Table 17.4 SAE viscosity grades for engine oils


Automotive Lubricant Specification and Testing



M.F. Fox

17.2.2 Performance Classifications and the ‘Tripartite’

The most influential world organisation defining and developing automotive lubricant qualities was the informal tripartite group of three large US organisations, SAE,

ASTM (‘American Society for Testing & Materials’) and the American Petroleum

Institute (API). Each organisation, with other interests beyond automotive lubricants, collaborated for many years, each with its defined role. The problem was that

individuals and companies were often represented on two, or even all three, of the


As engine ratings increased, a lubricant classification was needed and API introduced the ML, MM and MS system for various early 1950s spark ignition engine

operation service condition and an analogous DG, DM and DS system for diesel

engines. No performance standards were initially specified: therefore the system

was of limited utility, particularly as manufacturers tended to classify their products at the higher performance level. ASTM ‘sequence tests’ were then introduced

as more precise definitions of oil performance and engine service, API cooperating

with ASTM and SAE in 1969–1970 to establish new engine service classifications

for lubricants where:

– ASTM defined the test methods and performance targets,

– API developed the service letter designations and ‘user’ language and

– SAE defined the need and combined the information into an SAE ‘Recommended

Practice’ in the SAE Handbook for consumer use.

The current document is the ‘Engine Oil Performance and Engine Service Classification’ (other than ‘Energy Conserving’), SAE J183 JUN91,(5). API Engine

Service Classifications divide into the ‘S-’ lubricants series for passenger cars/light

trucks (gasoline engines) and ‘C-’ lubricants series for commercial, farm, construction and off-highway vehicles (diesel engines). Lubricants can meet more than one

classification, e.g. API SG/CD or CE/SG, thus the API SG category was formally

adopted in 1988, similarly the API CE category was adopted in 1988 and recommended by all American heavy duty engine manufacturers. Heavy duty diesel

engine specifications have been revised approximately every 4 years since API CF4 in 1990 up to API CJ-4 in 2006, the heavy duty diesel engine specification current

for four-stroke diesel engines at the time of writing. Similarly API SM is the present

passenger car engine test category. The API system is described in ‘Engine Service

Classification and Guide to Crankcase Oil Selection’, API Bulletin 1509, in its current technical bulletins.

API is not an approval body but certifies lubricant quality, developing its ‘Service

Symbol’ (Fig. 17.1) in 1983, issuing licenses to oil companies for promotion of their

lubricants. The symbol’s centre circle shows the lubricant SAE viscosity grade, the

outer ring upper half contains the API performance classification (only current performance qualities shown, obsolete performance levels may not be used). The outer

ring lower half indicates an ‘energy-conserving’ or fuel economy standard. API’s


Automotive Lubricant Specification and Testing


role has developed into its ‘engine oil licensing and certification system’ (EOLCS),

discussed later in this section.

Fig. 17.1 The API service


17.2.3 The US Military and the SAE Lubricants Review

Institute (LRI)

Lubricant manufacturers worldwide required their products be approved to the US

military MIL-L-2104, and subsequent MIL-L-46152, specifications. Few of these

approvals were for their ostensible primary purpose of US military supply tendering, the military approval process itself was of considerable value to the lubricants

industry due to its stringently objective reviewing procedure.

In 1977, approvals were placed with the SAE as the ‘Lubricants Review Committee’ of the Lubricants Review Institute (LRI), and this worked well for a decade.

Engine lubricant test policy changes and strengthened API classifications, described

below, gave lubricant companies and also end users more confidence, reducing the

need for US military approvals. The influence of the LRI diminished, and the US

military questioned the approval process cost-effectiveness and whether it should

source lubricants at the appropriate API quality as a ‘commercial item description’


17.2.4 Changes in the 1980s

The SAE, API and ASTM ‘tripartite’ arrangement gave the United States an established lead in engine lubricant quality standards for many years but various concerns

arose in the 1980s which led to change. The ‘tripartite’ constitutional framework

eventually became both a virtue and a weakness, for relevant SAE and ASTM

committees include automotive, lubricant and additive industry representatives who

might have conflicting organisational objectives.


M.F. Fox

The Motor Vehicle Manufacturers Association, MVMA, proposed a new

approach because new tripartite system lubricant specifications took 6/8 years from

proposal to agreement with the final performance requirements often being lower

than intended at the outset of such protracted programmes. This was both slow and

unacceptable, particularly when set against a rapid rate of change in the automotive

industry with MVMA’s new technologies such as computer-aided design/computeraided manufacturer, CAD/CAM, reducing new model development from 7 down to

3/4 years, now even shorter. MVMA was also concerned for the requirement to produce failure evidence, colloquially ‘a basket of failed parts’, before action was taken

by the lubricant industry. MVMA argued for a changed approach, to ‘prevent failure’ rather than ‘cure problems’ and to allow lubricant development to meet future

standards with future engines. A further problem was no defined field experience.

The situation came to a head in 1989/1990 when the OEMs unilaterally proposed

to develop their own specifications and approvals. The API argued that the existing

system worked well for users with few or no significant field problems. It also argued

that the industry sold lubricants to users with legal product liability and therefore,

they must make a major contribution to the definition of product quality for their

brand names. Both industries made significant concessions to resolve their differences.

17.2.5 American Chemistry Council, ACC, ‘Code of Practice’

Parallel to the very slow pace of the ‘tripartite’ process, criticisms were also made

of the definitions of ‘passing’ for lubricant quality tests. Essentially, should ‘pass’

mean ‘always able to pass’, or the ‘capability to pass has been demonstrated’, or

an intermediate position? – this is more than semantics, for when the poor precision of engine tests compared to laboratory bench tests is considered, the answer

is not self-evident. There was no requirement to pass each test every time or even

on average, the exception being UK MoD approvals always requiring the test sponsor/laboratory to state their intentions and formulations before an engine test and

to supply all results, pass or fail. Attempts to obtain a ‘pass’ for a particular formulation were strictly limited to two. Other specifying and approval authorities had

normally not required such information, including the much more influential US

military together with individual OEMs where it was not necessary to report failed

results. Only passing results, usually with relevant engine components, must be presented. The limit of only two engine lubricant tests is particularly restrictive if the

test concerned is:

imprecise or ‘bouncy’,

large business volumes are at stake, needing a price competitive formulation,

a new formulation has already had a lot of resource spent on it and

the particular (failed) test was close to the end of a long test sequence and reformulation to pass that test would be take too much time or expense.


Automotive Lubricant Specification and Testing


Incentives to undertake multiple engine lubricant tests are considerable, limited

in practice by the time for testing and the considerable costs entailed. This approach

can approve a formulation, which might not pass all tests first time at random

against specification, an unsatisfactory position. For some circumstances, lubricant

formulators could make multiple attempts at each engine test within a specification. Another concern is lubricant formulation where high-quality internationally

branded lubricant specifications may need up to 20 engine tests, together with bench

tests, all with conflicting formulation needs. It may be difficult for a formulator to

get new formulation approval at the first attempt and unreasonable to recommence

testing because a small change has been made to one component’s concentration in

a formulation. But what is then ‘reasonable’ in formally handling changes to formulation? Some agreed practices are established for United States and Europe to allow

controlled ‘running changes’ in a formulation under test, e.g.:

– US formulators follow the ACC Code of Practice and a running change in a formulation could be accepted without retesting or could require several tests to be

repeated, thus as examples:

– an increase in ashless dispersant level normally has a positive effect on sludge

performance, yet neutral in other tests,

– but increased mono-functional viscosity modifier would be detrimental to

diesel engine piston deposit control.

Base stock composition changes are not usually made without invalidating

approvals. Some base oil suppliers demonstrated interchangeability of base stock

sources, others regard this as unnecessary, making their own judgements on base

stock change validity. Different judgments have been made on the need to disclose

formulation changes by different formulating companies. Judgements to disclose

within an international company can be different for the geographical locations of

approval authorities and also the experience and character of a company’s continental operation.

Another pressure for change in the 1980s, separate from MVMA concerns, was

the very strong growth of ‘quality procedures’ resulting partly from the success

of Japanese industry and ISO 9000-series quality accreditation. This caused fresh

concerns about industrial lubricant formulation/testing practices. These views were

strongly argued at the 1989 CEC Symposium and drew serious interest in Europe.

The additives industry supported these concerns and established a (US) Chemical

Manufacturers Association (CMA) panel to write the ‘CMA Product Approval Code

of Practice’, implemented in 1992, which originally covered the engine tests in the

latest API ‘S’ category. In principle, other tests showing sufficient precision and

control could be added. The five main features of the ACC Product Approval Code

of Practice are:

1. Engine tests, registered with independent monitoring agencies prior to running,

are only run on ‘referenced (test) stands’ with established, accepted, statistical



M.F. Fox

2. Sponsors select the testing laboratory but not the individual test stand which must

normally be the ‘next available’ stand.

3. MTAC, as ‘Multiple Test Acceptance’ criteria, were introduced, where a lubricant must pass all controlled individual parameters on its first test. If a second

test is needed, then each mean parameter value must be a pass. For running

three or more tests, one complete test can be discarded and the mean parameter values from the remaining tests must pass. From experience, individual test

results can be adjusted for identified severity changes in the test procedure from

the lubricant test monitoring system using ASTM test monitoring centre control


4. Details of changes to original formulations made as ‘minor’ formulation modifications were documented in great detail. Now all users of the code had a consistent set of working rules.

5. A ‘candidate data package’ provides all of the test results together with an audit

trail to demonstrate the nature and validity of formulation changes, plus details

of all scheduled tests and severity changes.

The Code of Practice is voluntary but all major players have committed to all tests

initiated by them, and covered by the Code, are conducted in accordance with it.

17.2.6 EOLCS – The API Engine Oil Licensing

and Certification System

EOLCS, the (API) engine oil licensing and certification system, arose from the problems and conflicts previously described, and has five key elements:

1. Defined performance standards defined similarly to the ‘tripartite’ system, where

SAE, API and ASTM perform their previous traditional roles. If ASTM cannot

achieve consensus, there is provision for ILSAC to take over. The system defines

physical, chemical and performance characteristics of engine lubricants for API

‘SX’ and ‘CX’ specifications.

2. Engine test protocol requires that each engine lubricant test must be run according to the American Chemistry Council Code of Practice. Whilst use of the

code is generally voluntary, EOLCS mandates its use if the particular test

has been covered by the Code. In 2005 the tests covered were Sequences

IIIF, IIIG, IIIGA, IVA, VG, VIB, VIII; Caterpillar 1 K, 1MPC, 1 N, 1P, 1R,

C13; Mack T-8, T-8E, T-10, T-11, T-12; RFWT; Cummins M11, M11 EGR,

ISB, ISM; Detroit Diesel 6V92TA. Refer to the latest ACC Code of Practice

at: http://www.americanchemistry.com/sacc/bin.asp?CID=368DID=1361DOC=


3. A licensing procedure where lubricant marketers are responsible for product

performance and must certify that each viscosity grade of each brand meets

requirements. Detailed rules allow for base stock interchange and engine test

read across in certain circumstances from one viscosity grade to another.


Automotive Lubricant Specification and Testing


This is described in API 1509, the latest edition of which can be found at:



A sliding scale of fees, minimum $500/grade/company, with an extra $1000

for each 1 M (US) gallons sold above the first 1 M gallons (3.6 M l). The EOLCS

minimum royalty fee for licensure is $1,050 US for API members and $1,250 US

for non-members. Additionally, an annual fee of $0.0015 per gallon of licensed

motor oil after the first million gallons production of licensed oil will be assessed,

the latest on EOLCS at: http://www.api.org/certifications/engineoil/index.cfm.

4. Certification marks, two licensed marks were available:

First, the API symbol (Fig. 17.1), previously, which can be anywhere on the

packaging, with product details changing according to product nature and performance levels; second, the API certification mark, (Fig. 17.2), previously known

as the ILSAC certification mark, which must be on the front of the container.

This mark cannot be changed and can only be used if the product meets the current ILSAC performance level. If the product has the testing qualifications, the

marketing organisations can use either or both symbols.

5. Conformance audits applied to all licensed products. Manufacturers whose lubricants fail can be subject to enforcement penalties which range from licence suspension to removal of the product from sale.

Fig. 17.2 The API


17.2.7 Laboratory Petrol/Gasoline Engine Test Development

Automotive engine manufacturers test their products on ‘test beds/stands’ for the

further development of engines and provenance of their product. Caterpillar, as

described previously, evaluated lubricants and additives using the 1930s L-1 engine

tests and the L-4 (1942) petrol/gasoline Chevrolet engine test evaluated lubricants

for oxidation and viscosity increase. These tests were the basis for a later proliferation of specification tests mainly using commercial, already extant, engine designs,

usually the smaller versions.


M.F. Fox

Engine lubricant test development became very time consuming and even more

expensive at the same time as doubts increased of their relevance to real field service, particularly for single cylinder engines. Emphasis moved towards commercial

multi-cylinder engines of increasing size and complexity, parallel to commercial

engine development. But larger engines require larger test beds and power absorption dynamometers, more fuel for longer periods and more time for rating/rebuilding

than the previous smaller engines. Engine lubricant test evaluation costs have rapidly


17.2.8 The API ‘M’ Series of Lubricants

As described in Section 17.2.3, automotive power and range developed steadily

from the late 1940s/early 1950s into the 1960s. API defined a lubricant classification based on service use, the M-series of lubricants for light vehicles, ML (light

duty), MM (medium duty) and MS (severe duty). MS grades assumed light vehicle operations with frequent low temperature, lightly stressed, short journeys mixed

with occasional prolonged high temperature, long journeys. Different severities of

lubricant grades were not specified and lubricant manufacturers/marketers decided

which ‘M’ level applied for their product, hence as ‘MS’ was regarded as the ‘best’

grade, many lubricant formulations had this label irrespective of additive content or

base lubricant suitability, which was unpredictable across brands.

US OEM engine tests defined ‘MS’ quality lubricants in 1962, mandatory for

1964 warranties. ‘MS’ lubricant engine tests successfully defined products with

consistent oxidation resistance, wear performance, sludge formation and deposit

control which were demonstrable under controlled test cell conditions, demonstrating standards rapidly accepted worldwide, using the original ASTM test sequences,

Table 17.5. Europe added on some local manufacturer’s engine tests to the US OEM

engine test standards and requirements.

Table 17.5 The original MS quality test sequences

Sequence number








Low temperature, medium speed scuffing

Rust and corrosion at low temperatures

Oxidation and deposits at high temperatures

Scuffing and wear

Sludge at low and medium temperatures

1960 Oldsmobile V8

1960 Oldsmobile V8

1960 Oldsmobile V8

Chrysler V8 1962

1957 Ford Lincoln

The scuffing and wear aspects of Sequences I and IV were incorporated into

Sequences III and V, thus I and IV were dropped and only Sequences II, III and V

remained in (upwardly revised) severe forms, together with Sequence VI for energy

efficiency. IV has re-appeared, as also has a Sequence VIII.

The ASTM sequence series, and their subsequent developments, have responded

to rapidly increasing requirements of overall petrol/gasoline and diesel engine


Automotive Lubricant Specification and Testing


performance as increased energy densities, reduced emissions, increased fuel

economy and considerably extended service intervals.

17.2.9 Evolution of the API ‘SX/CX’ – Standard Series

External requirements of emission control technology, higher energy densities

and operating temperatures, increased fuel economy and extended service intervals stretched the newly established engine lubricant standards. The first automotive emission control device, the positive crankcase valve, PCV, recirculated

internal engine blowby as partially burned reactive fuel substances. Lubricants

were degraded more quickly and in ways which were potentially more difficult to

treat. Contemporary MS level lubricant quality was increased, various OEMs set

their increased standards and the sequence tests were revised with additional letters

attached, such as II-B, III-B, V-B. Whilst developed for a wide range of service conditions, these tests were inadequate for high-speed, high-load service such as towing

caravans and boat trailers for long distances and a new approach was needed.

The tripartite API, SAE and ASTM jointly introduced a robust new classification system, SAE J183, in 1970 to be readily extended or ‘open ended’.

Gasoline/petrol lubricants are ‘S-(X)’ prefixed, grafted onto the ‘M’ series

through ‘MS’ quality levels equivalent to ‘SD’, with ‘C-(X)’ series as parallel

diesel engine lubricants. The system has worked through formulation revisions to meet enhanced performance standards, through to the SM (2004) API

engine oil classifications for service-fill oils, the latest classifications being on


pdf. The progressive system has developed to meet increased technical demands

of internal combustion engines where formulations are adjusted, rebalanced and

improved to meet increased engine technology development. The issues have been

to meet increased anti-oxidation standards, reduced sludge formation, reduced

wear, maintenance of viscosity/viscosity indices, and reduced evaporative loss, a

relentless increase in lubricant quality, a historical account of API SX from ‘SA’ to

‘SJ’ is given in Ref. [1].

Similarly, successive diesel ‘C-(X)’ standards have improved to meet higher

energy densities, turbocharging, reduced piston deposits, lubricant consumption,

bore wear and ‘bore polish’ and black sludge formation, through to the ‘CJ-4’ series

in 2006. Standards initially changed to meet the use of higher fuel sulphur content,

>0.5%, whereas more recent fuel developments have moved towards very much

reduced levels of sulphur. Lubricant formulations have contributed to vehicle economy (US CAFE, Corporate Average Fuel Economy), ILSAC established energyconserving lubricant standards for all engines that may claim API EC, principally

addressed by the ASTM VI sequence fuel economy engine test.

The additive % mass in lubricant formulations, including VII, pour point

depressants and anti-foam agents, can total up to 20% of the total mass. ‘SX’

petrol/gasoline progressions have encompassed increased lubricant service change


M.F. Fox

intervals, the trend levelled in the mid-1990s but more recent developments show

a further increase up to 50 k km (or 32.5 k miles) in some cases in Europe, with

further increases to be expected, as:

– a steady increase in additive % total mass in formulations, but constrained by the

need for reduced ‘SAPS’,

– rise, fall and then rise again of metal sulphonate, disappearance of thiophosphonate and the decline in phenate detergents, then the move towards ‘Low SAPS’,

– levelling off and then decline of ZDDP, and (later) increase ‘other’ anti-oxidants,

to meet concerns for three-way catalytic converter fouling and an associated

reduction in effective life,

– decline and omission of ‘anti-rust’,

– the continual increase in engine energy densities from 1949 and

– reductions in engine lubricant working volume and also consumption.

17.2.10 Achievements of the Tripartite System

The US tripartite system has made substantial achievements since its inception. It is

striking that whilst dealing with and meeting the requirements described above, it

has contributed inter alia towards decreasing lubricant consumption by 80% overall.

In the same period average fuel consumption has also decreased by 43% and total

lubricant consumption over a 15,000 km service interval has decreased by 92%. The

US tripartite system has successfully responded to the initial challenge of specifying lubricant performance in vehicles; it has responded, and continues to respond

by approximately 4-year reviews, to meet the additional requirements for lubricant

performance specification introduced by environmental emission standards, particularly the low NOx and soot standards. The increased soot levels resulting from

changes in diesel engine combustion, together with increased service interval oil

changes and with the further requirement of fuel economy, have led to problems of

high-temperature deposits, ring sticking and oil thickening/dispersion. In turn, high

soot levels can lead to increased valvetrain and bearing surface wear. These issues

are addressed in the next subsections on the API CJ-4 and SM standards.

The API system, and similarly the ACEA system as will be seen in the next

section, have worked well because, overall, an integrated approach has been taken

involving developments in engine design, fuel and lubricant together. A range of

lubricant specifications are available for a range of engines and fuels which have

been developed over 10–20 years.

It is instructive to consider countries where such technical transitions have not

been so well managed. For the largest national lubricant market in the Middle East

[2], locally constructed vehicles are now complemented by more modern vehicles locally assembled by multi-national manufacturers to international standards,

together with imported vehicles built to the same international standards. The problem is that high levels of impurities in fuels rapidly degrade predominantly obsolete

lubricant formulations. Two-thirds of those lubricants for passenger car and light


Automotive Lubricant Specification and Testing


vehicles are API SC standard, declared obsolete by API a decade ago and not suitable for engines built after 1967. A further 26% of lubricants are graded SE, SF

and SG, also declared obsolete and not suitable for vehicles constructed after 1979,

1988 and 1993, respectively. For heavy duty diesel trucks, 50% of lubricant volume

is API CD (ca. 1955) and API CE (ca. 1985). Locally assembled European trucks

and buses are very popular and require at least API CI-4 plus (ca. 2002). Locally

manufactured light vehicles require at least API SL.

Fuel quality is the major problem, the official sulphur content of diesel is

10,000 ppm, i.e. 1%, probably higher in practice, whereas Europe and North America either have capped, or will shortly cap, diesel sulphur content at 10–20 ppm.

The very high sulphur fuel degrades lubricants very quickly so that service interval

lubricant drains for trucks average 4500 km (cf. 30,000–160,000 km in Europe) and

2000/2500 km for passenger and light vehicles (cf. 25,000 km in Europe). These fuel

quality levels are particularly active in degrading low SAPS oils, as for API SM. In

addition to sulphur, fuels also contain high levels of phosphorus which deactivate

the three-way catalytic converters of new vehicles within their first hour, or so, of


17.2.11 API C-(Series) Specifications for Heavy Duty Diesel

Engines, Through to API CJ-4

The API C-series specifications have evolved as:

Now obsolete

CA/B/C: for naturally aspirated engines built up to 1959, 1961, 1990, respectively,

CD: introduced 1955 for certain naturally aspirated and turbocharged engines,

CD-II: introduced 1985 for two-stroke cycle engines and

CE: introduced 1985 for high-speed, naturally aspirated and turbocharged

engines. Can replace CC and CD lubricants.


CF: 1994, for off-road, indirect-injection and other diesel engines including

those using fuel containing >0.5% sulphur. Can replace CD lubricants.

CF-2: 1994, for severe duty two-stroke engines, can replace CD-II lubricants.

CF-4: 1990, for high-speed, four-stroke, naturally aspirated and turbocharged

engines, can replace CD and CE lubricants.

CG-4: 1995, for severe duty, high-speed, four-stroke engines using fuel containing <0.5% sulphur. Required for 1994 emission standards, can replace

CD, CE and CF-4 lubricants.

CH-4: 1998, for high-speed, four-stroke engines designed to meet 1998 emission standards. Specifically formulated for fuel containing up to 0.5% sulphur w/w. Can replace CD, CE, CF-4 and CG-4 lubricants.

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2 The United States/North America Tripartite System

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