About

Choosing the correct lubricant is vital for mechanical longevity. However, viscosity standards vary by application. Automotive engine oils use SAE Crankcase grades (e.g., 5W-30), gearboxes use SAE Gear grades (e.g., 75W-90), and industrial hydraulics use ISO VG (e.g., VG 46). These numbers are not directly comparable; an SAE 50 engine oil has roughly the same viscosity as an SAE 90 gear oil. This tool acts as an equivalence chart calculator, allowing mechanics and engineers to cross-reference these disparate standards based on Kinematic Viscosity (centistokes, cSt) at operating temperatures.

Note: This tool approximates equivalence based on standard Viscosity Index (VI) assumptions. Always check the manufacturer's specific data sheet.

Formulas

There is no single mathematical formula to convert these grades, as they are defined by lookup tables (standards SAE J300 and ISO 3448). The tool compares the Kinematic Viscosity (mm²/s or cSt) ranges.

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Low Shear Viscosity @ 100°CHigh Shear Viscosity @ 150°C

Reference Data

SAE Crankcase (Engine)	Approx SAE Gear	ISO VG Grade	Viscosity @ 100°C (cSt)
SAE 20	75W	VG 46 / VG 68	5.6 - 9.3
SAE 30	80W / 85W	VG 100	9.3 - 12.5
SAE 40	90	VG 150	12.5 - 16.3
SAE 50	90 / 140	VG 220	16.3 - 21.9
SAE 60	140	VG 320	21.9 - 26.1

Frequently Asked Questions

Generally, no. Even if the viscosity is similar to SAE 40 or 50 engine oil, the additive packages (detergents vs. extreme pressure additives) are completely different. This tool matches viscosity flow rates, not chemical suitability.

"W" stands for Winter. The number before the W (5) describes how the oil flows at cold temperatures (cranking viscosity). The second number (30) describes how it flows at operating temperature (100°C).

No. ISO VG grades (e.g., 46, 68) represent the viscosity in cSt at 40°C. SAE grades focus on performance at 100°C. This tool correlates them by assuming a standard Viscosity Index (typically 95-100).