API classification for enfines
All serious oil manufacturers test their production in various international and national quality institutions where the API (American Petroleum Institute) and the ACEA (Association des Constructeurs Europeens d’Automobiles) are the most often recognized.API classification defines the oil quality by carrying out tests on it in the engine. The wear and cleanliness of cylinder walls, piston rings, bearings and gas distribution mechanisms, formation of burns and deposits, surface damages and the increase of oil acidity may be examined during the tests. This classification divides engine lubricants into two groups marked by two letters: S-lubricants for petrol engines and C-lubricants for diesel engines. A second additional letter (e.g. SJ, SL or CG, CH) indicates the quality class. The higher it is, the further the letter in the alphabet marks it, . e.g.: SL Class oil has better operational properties than SJ. Universal use lubricants are marked with general symbols, e.g.: SL/CF.
For petrol engines:
- specifications from SA to SH inclusive are not used any more;
- SJ – has come into force since 1996; test requirements are the same as for SH, however they are more resistant to vaporization and contain lower quantity of phosphorus;
- SL – adopted in 2001; test requirements are the same as for SJ, however they are more rigorous for oil consumption and the formation of burns at high temperature; some of them save fuel;
- SM – came into force in 2004; these lubricants are more resistant to acidity increase, formation of burns, better protection from wear, ensure an easy start at low temperatures during their whole period of service; some of them save fuel.
Higher quality oil than indicated by the manufacturer may always be used for petrol engines.
For diesel engines
- CA to CE inclusive are not valid any more;
- CF-4 – has replaced CE since 1990 lower oil consumption and cleaner cylinders;
- CF-2 – since 1994; for two-cycle diesel engines;
- CF – has replaced CD since 1994; for engines using fuel with a high sulphur content (0.4%). It protects pistons from deposits at high temperatures and protects bearings from corrosion. It is suitable for normally aspirated engines and diesel engines with turbo injection;
- CG-4 has replaced CE, CE and CF-4 since 1994; for diesel engines to whom more rigorous pollution requirements are applied;
- CH-4 – since 1998; for diesel engines to whom even more rigorous pollution requirements are applied;
- CI-4 – presented in 2002; for diesel engines with very rigorous pollution requirements; especially suitable for engines using an additional exhaust gas recirculation (EGR) system;
- CI-4 PLUS – presented in 2004; exceeds the requirements for CI-oil;
- CJ-4 – came into force in 2006; recommended for use in the newest heavily loaded low-pollution diesel engines using low sulphur content fuel, compatible with both diesel particulate filters (DPF) and EGR.
Higher quality oil than recommended by the manufacturer can be used in all four-cycle engines because higher quality oil ensures better protection of engine elements. It is necessary to take into consideration the manufacturer’s recommendations when selecting an oil for two-cycle diesel engines.