SAE Viscosity Grades
Engine Oil & Fluids · 7 specs
Direct Answer
SAE J300 is the universal standard defining engine oil viscosity grades. Multigrade oils (e.g. 0W-20, 5W-30) specify two metrics: a low-temperature Winter ('W') grade governing Cold Cranking Simulator (CCS) and Mini-Rotary Viscometer (MRV) pumpability at sub-zero temperatures (-40°C to -10°C), and a high-temperature 100°C kinematic viscosity (cSt) and High-Temperature High-Shear (HTHS) rating.
Source: SAE International Standard J300_202104 (Engine Oil Viscosity Classification) · Last reviewed Aug 28, 2026
Specs
| Standardization | SAE J300 / ASTM D445 / ASTM D5293 (CCS) / ASTM D4684 (MRV) |
| Winter 'W' Cold Cranking Limits | 0W: Max 6200 cP @ -35°C | 5W: Max 6600 cP @ -30°C | 10W: Max 7000 cP @ -25°C | 15W: Max 7000 cP @ -20°C |
| Winter 'W' Low-Temp Pumping (MRV) | 0W: Max 60,000 cP @ -40°C | 5W: Max 60,000 cP @ -35°C | 10W: Max 60,000 cP @ -30°C |
| 100°C Kinematic Viscosity (SAE 20) | 6.9 to <9.3 cSt (mm²/s) — Modern fuel-efficient gasoline engines (0W-20, 5W-20) |
| 100°C Kinematic Viscosity (SAE 30) | 9.3 to <12.5 cSt (mm²/s) — Universal all-around benchmark (5W-30, 0W-30) |
| 100°C Kinematic Viscosity (SAE 40) | 12.5 to <16.3 cSt (mm²/s) — European performance and diesel engines (0W-40, 5W-40) |
| Ultra-Low Viscosity (SAE 16 / 12 / 8) | SAE 16 (6.1-8.2 cSt), SAE 12, SAE 8: Ultra-thin oils for next-generation hybrid powertrains |
High-Temperature High-Shear (HTHS) Viscosity
While 100°C kinematic viscosity measures oil flowing through a gravity tube, HTHS viscosity (ASTM D4683, tested at 150°C and 10^6 s^-1 shear rate) simulates the extreme shear stress between crankshaft journals and engine bearings under heavy wide-open throttle. Oils must meet minimum HTHS limits (e.g. ≥ 2.6 mPa·s for SAE 20, ≥ 3.5 mPa·s for heavy-duty European A3/B4 oils) to prevent metal-to-metal bearing contact.