High Temperature High Shear viscosity (HTHS)

HTHS (High Temperature High Shear) Viscosity (100ml)this is a relatively new oil specification test used to determine how well oils perform under extreme conditions e.g. where the temperature and friction is highest. Low HTHS oils give the best fuel economy as the oil is thinner and provides less energy to rotate the bearing shaft, but provides least protection against wear.  A high HTHS oil gives the best wear protection, but a poorer fuel efficiency. A table of the ACEA-2012 specification requirements is listed below. Traditionally, the test is performed at 150OC, but some of the newer fuel efficiency testbed testing now measures at 100OC as well.

LearnOilAnalysis Summary of ACEA 2012 HTHS data
Test A1 / B1 A3/B3 A3 / B4 A5 / B5 C1 C2 C3 C4 E4 E6 E7 E9
Viscosity at 150OC and 106 s-1 shear rate (mPa.s)

≥ 2.9 and ≤ 3.5;

On XW20 ≥ 2.6

≥ 3.5 ≥ 2.9 & ≤ 3.5 ≥ 2.9 ≥ 3.5 ≥ 3.5