Conventional oil was developed alongside the invention of the combustion engine; every other oil developed to lubricate engines stems from this petroleum-based oil. Since the early days of the automotive industry, conventional oil has been advanced through chemical engineering to improve its performance within the engine's extreme environment. Today's conventional oil continues to lubricate many engines and needs to be changed every 3,000 to 5,000 miles. 

This type of oil requires petroleum to produce and has a much higher percentage of synthetic base stock and additives than conventional. We like to think of semi-synthetic oil as a simple mixture of the two but it is not quite that easy to produce as this oil requires more processing than conventional. Semi-synthetic oil needs change service every 5,000 to 7,500 miles.

This oil does not contain any crude petroleum and is manmade from synthetic base stocks. Beyond the synthetic oil, it also contains additives that help extend degradation caused by extreme friction and heat. This type of oil needs to be changed every 7,500 to 10,000 miles.