HTHS viscosity – stability under high temperature and shear stress
The HTHS viscosity (High Temperature High Shear) indicates how stable an engine oil is at high temperatures and under high shear stress. It is measured at 150 °C under simulated engine conditions and given in mPa-s (millipascal seconds). The value shows whether the oil can maintain a stable lubricating film even under extreme stress – to protect bearings, pistons and valve trains.
What does the HTHS viscosity tell you about your engine oil?
In highly stressed engine areas – such as at high engine speeds, full load or long highway journeys – enormous temperatures and shear forces are generated. Oils with too low HTHS viscosity can become too thin under these conditions, which leads to friction, loss of performance and increased wear.
BASINOL engine oils are formulated to achieve the optimum HTHS value for their area of application – for reliable protection with maximum performance.
What is a “good” HTHS value – and why is it relevant?
A “good” HTHS value depends on the engine concept and the manufacturer’s specifications. For many European vehicles, the ideal value is ≥3.5 mPa-s. This value ensures that the oil retains a stable lubricating film thickness even under extreme loads. Modern “fuel economy oils” such as 0W-20 or 0W-16 sometimes have lower HTHS values – however, these can only be used in approved engines.
How does the HTHS viscosity differ from the SAE viscosity class?
The SAE class (e.g. 5W-30) describes the general fluidity of an oil in cold and hot conditions, but not its stability under high shear loads. The HTHS viscosity, on the other hand, is a practical additional specification that shows you whether the oil remains stable even under heavy loads. Two oils with the same SAE class can therefore have different HTHS values – and therefore different levels of protection.
When is an oil with a high HTHS viscosity useful?
A high HTHS value is particularly recommended for sporty driving, high continuous loads (e.g. trailer operation) or for vehicles with powerful turbo engines. Here, a stable oil protects against wear, oxidation and oil consumption. BASINOL offers both classic high-performance oils with high HTHS stability and modern low-HTHS formulations for specific vehicle requirements.
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