Engine oil is the lifeblood of your car. It reduces friction and wear, helps manage engine heat and protects against the effects of high temperatures and damaging contaminants. If you have the right type of engine oil and the correct amount, you stand a better chance avoiding expensive motor repairs.
Different oils have different thicknesses also known as “viscosity”. For example, a viscosity rating on a bottle of oil might be written as 5W-40. The “5W” refers to the thickness of the oil while the engine is cold- the lower the number the better it is. The “40” refers to the thickness of the oil at operating temperature. The lower the number, the more efficiently your car will run.
API (AMERICAN PETROLEUM INSTITUTE) SPECIFICATIONS
The API specifications are two-letter rating beginning with:
“S” for Service (petrol)
“C” for Commercial (diesel)
The second letter designates the oil’s quality standard, beginning with the letter “A”. The further along the alphabet, the higher the oil’s quality. So SL performs better than SA. The current highest available standard s SN for petrol engines and CJ-4 for diesel engines.
Some oils meet standards for both petrol and diesel engines and will be marked with a dual specification, for example SL/CF.