TemperatureThe primary threat to an engine is temperature. Cold or hot, the wrong temperature at the wrong time will wreck a car engine. Oil is the lifeblood that keeps an engine running despite this factor.
Engine oil is used to prevent friction and heat from causing engine damage. If you have a vintage car or an old engine that needs to work in cold climate, temperature becomes a real issue for you. It stops parts from grinding together and it distributes engine heat quickly.
Historically, mineral oils had limitations with the amount of heat they could handle. However, both mineral and synthetic oils designed today are more than adequate to protect engine in the coldest winters and hottest summers. So this issue no longer represents major influence in oil decisions it once did. Synthetic oils are still able to run at higher temperatures overall, though.
Molecular DifferenceThe fundamental makeup of synthetic oils is entirely different from mineral oils. Being fabricated in an artificial process, synthetic oils are not as chaotic as mineral oil at the molecule level. Their structure is uniform which allows synthetic oils to maintain structure under much higher heat stress. Mineral oil molecules are random and different, breaking down quicker under heat limitations.
Chemical MixesMineral oil when fabricated is a byproduct of heating up crude, raw oil from the ground. This byproduct, once refined, is then mixed with cleaners and other chemicals to help protect engine parts. The final product is packaged and sold to consumers. All of these processes add extra materials that end up ultimately adding to sludge in the oil pan once broken down.
Synthetic oil is fabricated cleanly in its original creation. The result is a less polluted oil that goes into the car engine.