Engine oil viscosity that is too low can cause serious wear. Insufficient viscosity reduces oil film strength and increases metal to metal contact.
Low viscosity oils must only be used where the engine design and manufacturer specification permit them.
Oil film strength and load capacity
If viscosity is too low:
- Oil film thickness is reduced
- Bearing and cam wear accelerates
- Component fatigue increases
Effect on oil pressure
Low viscosity oil can reduce oil pressure and compromise lubrication at critical points.
Increased oil consumption
Lower viscosity oils are more likely to pass piston rings and valve guides, increasing consumption and deposits.
Thermal and mechanical stress
Reduced viscosity limits heat absorption and load cushioning, shortening component life.
When lower viscosity may be acceptable
Only where specified by the manufacturer and supported by engine design.
Frequently asked questions
Is thinner engine oil always more efficient
No. Efficiency gains only apply where engines are designed for it.
Can low viscosity oil cause engine damage
Yes, if used outside specification.
Related reference pages
Does engine oil viscosity really matter
What happens if engine oil viscosity is too high