Viscosity measured simulator#

The measured number from the ASTM D4683 test gives the temporary viscosity loss of a lubricant under high shear at elevated temperatures representative of engine operating conditions. It has also been found to relate to fuel economy which is why it has become such a focal point today. HTHS viscosity measured by ASTM D4683 correlates to the viscosity providing hydrodynamic lubrication in light-duty and heavy-duty engines. The rotor experiences a reactive torque to the oilвЂ™s resistance to flow (viscous friction) and this torque response level is used to determine the HTHS viscosity.

Viscosity measured simulator#

One method used to measure HTHS viscosity is ASTM D4683, officially called the Standard Test Method for Measuring Viscosity of New and Used Engine Oils at High Shear Rate and High Temperature by Tapered Bearing Simulator Viscometer at 150 вЊ.Д®ngine lubricant is introduced between a rotor and a stator at the test temperature of 150вЊ. So, the oil must be thick enough to maintain separation of the critical moving parts but thin enough to allow for fuel efficient operation. What is essential is the correct balance of support as well as ease of movement. Conversely, if the oil is too thin, then you sink to the bottom. If the film is too thick, you can barely move and must use more energy. One way to think of HTHS is to think of the protective oil film as if you are trying to swim.

The focus on high temperature high shear (HTHS) is gaining momentum as it is regarded as the parameter of the viscosity grade classification that best predicts fuel efficiency and more accurately mimics engine lubricant behavior in increasingly severe operating conditions.