SAE (oil viscosity grades)

SAE stands for the Society of Automotive Engineers (now SAE International), a US-based standards body. Riders meet the name mainly on oil labels, because the SAE J300 standard defines engine oil viscosity grades used worldwide.

In a grade such as 10W-40, the first number with W (winter) shows how easily the oil flows when cold, and the second shows its thickness at normal operating temperature (100 °C). A lower W number helps cold starts, and the second number should match what the manufacturer specifies. Fork oils also use 'weight' numbers like 5W or 10W, but these are not directly comparable between brands.

For bikes with a wet clutch, also check the JASO MA/MA2 rating, which confirms the oil will not make the clutch slip.