ACEA & API specifications
Independent standards provided by the American Petroleum Institute (API) and/or the Association des Constructeurs Européens d’automobiles (ACEA) should be noted to determine and compare oil qualities.
API petrol specifications range from SG (1989), SH (1993), SJ (1996), SL (2001), SM (2004) and SN (2010). In many cases, API grades are backwards-compatible, so an older engine that requires an Sg-specification oil should be able to tolerate an SJ lubricant of the same viscosity. Diesel API gradings of CH-4 (1998), CI-4 (2002), CJ-4 (2010) and CK-4 (2017) are current. The earlier CA, AB, CD, CE, CF and CG standards are obsolete, although you may still see them quoted.
ACEA grades consist of ‘A’ for petrol and ‘B’ for diesel and are usually not backwards-compatible, because they are structured with separate classes and categories for oils with different specifications. The current standards are: A3/B3 and A3/B4. The latest A5/B5 oils are for the lower viscosity types. C grade oils are intended for low SAPS blends, to protect particulate filters, and consist of C1, C2, C3 and C4 grades. ACEA C5 is suited for the latest generation of fuel-economy 0W-20 and 5W-20 oils.
Manufacturer specifications are numerous. Should one be provided in your car’s literature, use an oil that complies with the relevant code.