ISO 18335:2024 details a process for measuring the dynamic viscosity, η, and density, ρ, which are essential for calculating the kinematic viscosity, ν, of middle distillate fuels, fatty acid methyl ester (FAME) fuels, and their mixtures, up to a 60% blend with middle distillate fuels, as well as lubricating oils (such as base oils and formulated oils) and synthetic substances. The method employs a constant pressure viscometer. The kinematic viscosity range that this test method addresses is from 0.5 mm²/s to 2,000 mm²/s, with a precision of 1.0 mm²/s to 1,286 mm²/s at 40 °C and from 3.0 mm²/s to 157 mm²/s at 100 °C.
The outcome derived from the procedure outlined in this document is contingent upon the rheological behavior of the sample. The document primarily applies to fluids that exhibit a proportional relationship between shear stress and shear rate (Newtonian flow). Nevertheless, when viscosity varies significantly with shear rate, comparisons with other measurement techniques are only valid under similar shear rate conditions.
