HTHS viscosity*

Test instrument: Tapered Bearing Simulator
Sample quantity: 100 ml
Unit: mPas
Test result: High Temperature - High Shear - Viscosity
Analysis for: Engine oils
Brief description: Der Tapered Bearing Simulator is a specialised visometer for the determination of the viscosity at high temperature and high shear rate. It consists of a tapered rotor and stator. The unit is heated to 150°C. A shear rate of 1*106s-1 is generated due to the rotation. The oil sample to be tested is filled into the gap between rotor und stator. The rotor experiences a reactive torque to the liquid’s resistance to flow. This torque is used to determine the viscosity. 

The HTHS viscosity is a measure for the performance of an oil under conditions similar as in automotive and heavy-duty engines, namely at high temperature and rotation speed. Stable lubrication can be maintained even under these condition with oils having a sufficient HTHS viscosity. The ACEA sequences for engine oils therefore define limit values for the HTHS viscosity.

The regular HTHS viscosity is >= 3,5 mPas and required in sequences A/B 3,4 und C 3,4. Reduced HTHS viscosity is between 2,9-3,5 mPas and required in sequences A/B 1 und A/B 5. The sequences C1, 2 require a HTHS viscosity >= 2,9 mPas. The lowest HTHS viscosity between 2,6-2,9 mPas is required in sequence C5. 

Underlying test standard: ASTM D4683