21/10/2026
LOW HTHS VISCOSITY vs HIGH HTHS VISCOSITY — UNDERSTANDING THE SCIENCE BEHIND MODERN ENGINE PROTECTION.
Not all engine oils are engineered to deliver the same viscosity characteristics under extreme operating conditions. One of the most critical parameters is HTHS (High-Temperature High-Shear) viscosity, which measures an oil's dynamic viscosity at 150°C under a high shear rate of approximately 10⁶ s⁻¹, expressed in mPa·s.
HTHS viscosity plays a crucial role in balancing fuel efficiency, hydrodynamic oil-film thickness and engine protection.
🔵 LOW HTHS | EXAMPLE - PRINCE FSe SAE 0W-16
Engineered for gasoline engines of the latest generation specifically designed to operate with lower-viscosity lubricants.
• Lower HTHS viscosity helps reduce hydrodynamic friction and pumping-related energy losses, supporting significantly improved fuel efficiency.
• Optimised for engines designed with appropriate bearing clearances, lubrication systems and thermal management.
• SAE 0W-16 oils generally operate within an HTHS range of 2.3 to less than 2.6 mPa·s, in accordance with SAE J300 and ILSAC GF-6B.
🟡 HIGH HTHS | EXAMPLE - PRINCE FS1 SAE 5W-40
Developed for high-performance engines requiring greater oil film thickness under elevated temperatures and mechanical loads.
• Higher HTHS viscosity supports thicker hydrodynamic lubricant films under comparable operating conditions.
• Helps maintain oil film separation in heavily loaded components where the engine manufacturer specifies higher-viscosity engine oils.
• SAE 5W-40 oils require an HTHS viscosity of at least 3.5 mPa·s under SAE J300.
SO, DOES HIGHER HTHS ALWAYS MEAN BETTER PROTECTION?
Not necessarily.
Higher HTHS viscosity can improve oil film thickness and strength, but may increase viscous friction. Conversely, lower HTHS viscosity can improve mechanical efficiency, provided the engine is specifically engineered and approved for its use.
The correct HTHS viscosity is determined by engine design, operating requirements and manufacturer specifications — not simply by choosing thicker or thinner oil.
DIFFERENT VISCOSITIES. ENGINEERED FOR THE RIGHT PROTECTION.