These define three categories of lubricants identified by a two-letter code. The first distinguishes the engine for which it is intended: S means Service (petrol vehicles), C means Commercial (diesel vehicles), G for transmissions.
The second letter indicates the performance level: the further down the letter is in the alphabet, the higher the performance level. The latest specification for petrol vehicles is API SL while for diesel vehicles recently API specifications API CH-4 and CI-4 have been reached.
The tests required by the API, from SH onwards, are carried out following the rules of the CMA protocol (engine test control, formulation control, data control).
To obtain this classification, a lubricant must pass four engine tests, which consider:

  • the increase of the engine oil temperature in service
  • the lengthening of the interval between oil changes established by the manufacturers
  • engine performance research
  • strictness of environment protection standards
  • reduction of fuel consumption due to low viscosity (only for "Energy conserving" oils)

API "S" SPECIFICATIONS, for petrol engines

API SG For petrol engines of cars and light commercial vehicles starting from 1989. SG oils have better features than SF in terms of resistance to the formation of deposits, protection against wear and resistance to corrosion.
API SH Same features as SG but more stringent test conditions.
API SJ Engine oil of SH level, but developed in accordance with APY certification systems following multiple test criteria.
API SL Born on July 2001, intruduces limits in terms of stability to oxidisation, deposit control at high temperatures, reduction of volatility and consumption rates.
API SM Valid from November 2004, it asks for tougher tests about stability to oxidation, deposit control, performances at low temperatures.

With regard to OMVs, most Selenia lubricants have passed this specification:


API "C" SPECIFICATIONS, for diesel engines

CF For diesel engines with indirect injection and for other diesel engines which use a broad range of lubricants, including those with a high sulphur content (over 0.5 wt.). Control on deposits on the pistons, wear and corrosion of the bearings is important for these engines, which may be naturally aspirated, turbo-charged and high performance turbo-charged. The oils for these functions began to exist in 1994 and can be used when specification CD is recommended.
CF-2 Two-stroke diesel heavy-duty engines. Typical for two-stroke diesel engines, which require effective control on the cylinders, rings and deposits. The oils designated for this type of service began to exist in 1994 and can be used also when specification CD-II is recommended. They do not necessarily meet the requirements of specification CF or CF-4 even if they do have to pass these tests as well.
CF-4 Diesel engines 1990. Typical high speed service, 4-stroke engines. It exceeds the requirements of specification CE, providing more control on oil consumption and deposits on pistons. These oils ought to be used instead of the oils in category CE. Ideal for long journeys and harsh conditions of use. When combined with the appropriate S category, they can also be used for petrol engines and light diesels (cars, light vehicles, vans) if recommended by the manufacturer.
CG-4 Diesel engines in harsh operating conditions 1994. This specification describes oils for use in high-speed diesel engines both with applications under harsh motorway conditions (fuel with 0.05% of sulphur) and off the motorway (less than 0.5% sulphur in the fuel). They provide high control on deposit on the pistons at high temperatures, wear, corrosion, stability to oxidisation, accumulation of soot and foams. Specific oils for engines built to meet the used oils emission standards of 1994 and for engines that require API CD, CE and C-4. These oils began to exist in 1994.
CH-4 Diesel engines in harsh operating conditions 1998. Ideal oils for high speeds, 4-stroke engines, which meet the 1998 used oil emission standards and designed to use diesel fuels with sulphur content of up to 0.5%. These oils have higher performance than those that meet API CF-4 and API CG-4.
CI-4 Diesel engines in harsh operating conditions 2002. Oils for use at high speed, 4-stroke diesel engines designed to meet the 2004 used oil emission standards to be implemented in October 2002. To be used with fuels with sulphur content up to 0.05%. These oils are effective in supporting engine life when EGRs are used with other emission-related components. It offers excellent protection against wear, stability at high and low temperatures, protection against soot, piston deposit and foam control, loss of viscosity. These oils have higher performance than API CH-4, CG-4 and CF-4 oils and can be used in engines for which these API categories are foreseen.

Technical Manual - © FL Selenia S.p.A.