Engine Oil Specifications are important as these indicate the performance of the oil and whether they have met or passed the latest tests, or whether the formulation is effectively obsolete or out of date. There are two specifications that you should look for on any oil bottle and these are API (American Petroleum Institute) and ACEA (Association des Constructeurs Europeens d’Automobiles) all good oils should contain both of these, and an understanding of what they mean is important.

API

This is the more basic as it is split (for passenger cars) into two catagories. S = Petrol and C = Diesel, most oils carry both petrol (S) and diesel (C) specifications.

For Petrol Engine Oil

SG – Introduced 1989 – has much more active dispersant to combat black sludge.

SH – Introduced 1993 – has same engine tests as SG, but includes phosphorus limit 0.12%, together with control of foam, volatility and shear stability.

SJ – Introduced 1996 – has the same engine tests as SG/SH, but phosphorus limit 0.10% together with variation on volatility limits

SL – Introduced 2001 – all new engine tests reflective of modern engine designs meeting current emissions standards

SM – Introduced November 2004 – improved oxidation resistance, deposit protection and wear protection, also better low-temperature performance over the life of the oil compared to previous categories.

Note:
All specifications prior to SL are now obsolete and, although suitable for some older vehicles, are more than 10 years old, and do not provide the same level of performance or protection as the more up to date SL and SM specifications.

For DIESEL Engine Oil

CD – Introduced 1955 – international standard for turbo diesel engine oils for many years, uses single cylinder test engine only

CE – Introduced 1984 – improved control of oil consumption, oil thickening, piston deposits and wear, use additional multi-cylinder test engines

CF4 – Introduced 1990 – further improvements in control of oil consumption and piston deposits, uses low emission test engine

CF – Introduced 1994 – modernised version of CD, reverts to single cylinder low emission test engine. Intended for certain indirect injection engines

CF2 – Introduced 1994 – defines effective control of cylinder deposits and ring face scuffing, intended for 2 stroke diesel engines

CG4 – Introduced 1994 – development of CF4 giving improved control of piston deposits, wear, oxidation stability and soot entrainment. Uses low sulphur diesel fuel in engine tests

CH4 – Introduced 1998 – development of CG4, giving further improvements in control of soot related wear and piston deposits, uses more comprehensive engine test program to include low and high sulphur fuels

CI4 – Introduced 2002 – developed to meet 2004 emission standards, may be used where EGR ( exhaust gas recirculation ) systems are fitted and with fuel containing up to 0.5 % sulphur. May be used where API CD, CE, CF4, CG4 and CH4 oils are specified.

Note:
All specifications prior to CH4 are now obsolete and, although suitable for some older vehicles, are more than 10 years old and do not provide the same level of performance or protection as the more up to date CH4 & CI4 specifications.

ACEA

This is the European equivalent of API (US) and is more specific in what the performance of the oil actually is. A = Petrol, B = Diesel and C = Catalyst compatible or low SAPS (Sulphated Ash, Phosphorus, and Sulphur).

Unlike API the ACEA specs are split into performance/application catagories as follows:

A1 Fuel economy petrol
A2 Standard performance level (now obsolete)
A3 High performance and/or extended drain
A4 Reserved for future use in certain direct injection engines
A5 Combines A1 fuel economy with A3 performance

B1 Fuel economy diesel
B2 Standard performance level (now obsolete)
B3 High performance and/or extended drain
B4 For direct injection car diesel engines
B5 Combines B1 fuel economy with B3/B4 performance

C1-04 Petrol and light duty Diesel engines, based on A5/B5-04 low SAPS, two-way catalyst compatible.
C2-04 Petrol and light duty Diesel engines, based on A5/B5-04 mid SAPS, two way catalyst compatible.
C3-04 Petrol and light duty Diesel engines, based on A5/B5-04 mid SAPS, two-way catalyst compatible, higher performance levels due to higher HTHS.

SAPS = Sulphated Ash, Phosphorous and Sulphur.

Put simply, A3/B3, A5/B5 and C3 oils are the better quality, stay in grade performance oils.