Most of the people believe that the only function if motor oil is engine lubrication. But engine oils must cope with many more tasks.
There are at least five main functions of engine oil:

Cool          - absorbs heat as it is circulated, cooling the engine.

Lubricate  - creates a viscous barrier between moving parts that reduces friction, which means less heat and longer life for those parts.

Clean        - small particles of dirt or other contaminants are suspended in oil and carried away to be filtered out.

Seal          - helps to seal the gap between pistons and cylinder walls so that compression is more effective and power is not lost during combustion.

Protect      - coats metal parts to provide a protection layer against corrosion/rust.

All those functions fulfill Maxima motor oils with high safety margin.