Start with the viscosity grade
Labels such as SAE 0W-20, 5W-30 or 10W-40 describe multigrade viscosity performance. The number before W relates to low-temperature requirements; the second number relates to high-temperature viscosity classification.
SAEviscosity classification system
5Wlow-temperature grade
30high-temperature grade
Performance specifications
Viscosity alone is not enough. Oil containers may also carry API, ACEA, ILSAC and vehicle-manufacturer approvals. These address performance areas such as wear, deposits, oxidation, emissions-system compatibility and fuel economy.
Manufacturer approvals
Many engines require a specific OEM approval in addition to a viscosity grade. Two oils with “5W-30” on the front can have very different additive systems and approvals.
Use the exact oil specification stated for the engine, market and service regime. Do not select oil from viscosity alone.