ISO VG Grades for Industrial Oils — A Quick Reference

Industrial oils — hydraulic, gear, compressor, turbine — don't use the SAE automotive grading system. They use ISO VG (International Organization for Standardization Viscosity Grade), a simpler, single-number scale that's easy to misread if you're used to automotive grades.

How the ISO VG number works

The number in a grade like ISO VG 46 is the oil's kinematic viscosity in centistokes (cSt), measured at exactly 40°C — and that's it. Unlike SAE's two-number, cold-and-hot system, ISO VG describes performance at one single, standard reference temperature, because most industrial equipment runs in a much more stable, controlled temperature environment than an engine does.

The standard grade ladder

ISO VG grades run in a fixed, standardized sequence: 2, 3, 5, 7, 10, 15, 22, 32, 46, 68, 100, 150, 220, 320, 460, 680, 1000, 1500. Each step up is roughly 50% more viscous than the one before it. In practice, most industrial buyers only ever deal with a handful of these:

• ISO VG 32 / 46 / 68 — the most common hydraulic oil grades, used across excavators, presses, lifts, and general industrial hydraulic systems. VG 46 is the most widely used single grade worldwide.
• ISO VG 100 / 150 / 220 — heavier-duty gear oils and slower-moving industrial gearboxes.
• ISO VG 32 (turbine) — a distinct, higher-purity turbine oil formulation, not to be confused with a general hydraulic VG 32 — turbine applications have much stricter oxidation-stability and water-separation requirements.

Don't assume equipment manuals mean SAE

A common mistake for buyers newer to industrial lubricants: an equipment manual that just says "grade 46" almost always means ISO VG 46, not anything related to the SAE scale — the two systems share no relationship. Always confirm which system a spec sheet or manual is referencing before ordering.

Getting it right the first time

If you're not certain which ISO VG grade a specific machine needs, share the equipment make/model or the existing spec sheet with us — this is exactly the kind of question our upcoming AI RFQ tool and our team can both answer directly, rather than guessing from a generic manual.