Abstract: Lubricating oil composition comprising a major proportion of a mineral lubricating oil and, as viscosity index improver, a hydrogenated block copolymer or olefin copolymer functionalized by the presence of carboxyl groups attached to the polymer chain by a sulphonamide linkage.

Abstract: A method and apparatus for measuring the load bearing capacity of engine oils under determined temperatures and shear rates. An eccentrically rotating cylindrical shaft (rotor) is used in a cylindrical journal bearing (stator) so arranged that the stator can be displaced from the center of rotation by a known amount. Measurements are made of minimum gap between the rotor and stator and of the force required to maintain the eccentrically rotating loaded shaft at a position such that the oil in the gap between rotor and stator achieves a shear rate between 1.times.10.sup.5 and 1.times.10.sup.7 s.sup.-1, typically 1.times.10.sup.6 s.sup.-1.