The invention provides oil-soluble multivalent metal ion salts of a compound of the formula XNR.sup.1 R.sup.2, in which R.sup.1 and R.sup.2 are the same or different and each are selected from hydrogen and hydrocarbon based radicals having from 1 to 30 carbon atoms, X is an acyl radical of an aromatic ortho-hydroxy carbozxyic acid having a ring substituent which is a hydrocarbon based radical having at least 4 carbon atoms, a process for their preparation, and their use, as additives, in lubricating oils.
A method for testing a sample for soot-related viscosity increase comprising: (a) preparing the sample which comprises a major amount of an oil of lubricating viscosity, (b) measuring the viscosity of the sample (c) preparing a stable sample/paste dispersion of the sample and a carbon black paste, (d) equilibrating the sample/paste dispersion, and (e) measuring the viscosity of the sample/paste dispersion, and a method for predicting physical effects of soot-loading on a sample in a test which measures viscosity increase comprising: (1) measuring viscosity increase for a series of reference fluids in the test, (2) measuring viscosity increase for the series of reference fluids in a method having steps (a) to (e), (3) developing a curve, (4) evaluating the sample using the method having steps (a) to (e), and (5) interpolating a viscometric effect for the sample using the curve.
There are disclosed low sulphur content middle distillate fuel oils which have their lubricity properties greatly improved through the addition of a compound having at least one substituted aromatic ring system wherein the substituents are one or more aliphatic hydrocarbyl groups having 14 to 36 carbon atoms, one or more hydroxyl groups or a derivative thereof and one or more amide groups.
