There are three main types of engine oil: mineral oil, semi-synthetic oil and fully synthetic oil.
Mineral oils are made from naturally occurring crude oil which is refined and processed to remove waxes and impurities. Mineral oils tends to be found in the thicker viscosity grade of engine oils. Mineral oil lasts 5000 kilometres.
Semi synthetic or part synthetic oils are a blend of both mineral and synthetic oils. They provide better performance, protection and fuel economy than mineral oils, but not as good as a full synthetic. Semi-synthetic oil is good for 10,000 kilometres.
Fully Synthetic oils are chemically synthesised to meet the exacting demands of modern engines. This makes them more expensive to produce, but because they are tailor-made they provide the best performance, protection and fuel economy. They also remain stable at very high temperatures and fluid at very low temperatures. Fully synthetic oil has a 20,000 kilometre lifespan.