HTHS Viscosity

Description

A critical indicator for modern engines, evaluating lubricating film strength and the oil's ability to protect parts from wear at temperatures of 150 °C and extreme shear rates.

In the world of modern turbocharged engines and strict environmental regulations, classic kinematic viscosity is no longer sufficient. The RENA laboratory offers HTHS (High-Temperature High-Shear) analysis — an advanced method for evaluating how your motor oil will behave in the hottest and most heavily loaded friction nodes, such as crankshaft bearings or camshaft lobes. This analysis allows fleets to safely transition to energy-saving low-viscosity oils while avoiding catastrophic equipment wear. The HTHS test simulates fluid dynamics in a hydrodynamic journal bearing operating at its limits. During the test, the oil sample is subjected to a temperature of 150 °C at a colossal shear rate of 10^6 s^-1 (one million reciprocal seconds). Under such extreme conditions, the long molecules of polymeric thickeners (VI improvers) contained in multigrade oils begin to deform, stretch, and sometimes physically break, leading to a temporary or irreversible drop in viscosity. Using a specialized tapered bearing simulator (rotational viscometer), the instrument measures the torque (resistance) that the oil exerts on the rotor as it spins at high speed. The higher the resistance, the higher the HTHS value, and the thicker and stronger the lubricating film remains in a real engine during peak loads.